Ruby Polars

https://www.rubydoc.info/gems/polars-df
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Ruby Polars provides blazingly fast DataFrames for Ruby, leveraging the high-performance Polars...
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### Initialize DataFrame for examples

Source: https://www.rubydoc.info/gems/polars-df/Polars/DataFrame%3Amap_rows

Setup code used for the subsequent map_rows examples.

```ruby
df = Polars::DataFrame.new({"foo" => [1, 2, 3], "bar" => [-1, 5, 8]})
```

--------------------------------

### Initialize Series for chunking examples

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series%3Achunk_lengths

Setup two Series objects to be used in subsequent concatenation examples.

```ruby
s = Polars::Series.new("a", [1, 2, 3])
s2 = Polars::Series.new("b", [4, 5, 6])
```

--------------------------------

### Example code block

Source: https://www.rubydoc.info/gems/polars-df/Polars/Catalog/Unity/TableInfo

A generic code block example found in the documentation.

```ruby
5
6
7
```

--------------------------------

### row_index Usage Examples

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions

Examples demonstrating how to generate row indices in DataFrames and aggregations.

```ruby
df = Polars::DataFrame.new({"x" => ["A", "A", "B", "B", "B"]})
df.with_columns(Polars.row_index, Polars.row_index("another_index"))
```

```ruby
df.group_by("x").agg(Polars.row_index).sort("x")
```

```ruby
df.select(Polars.row_index)
```

--------------------------------

### select Usage Example

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions

Example of using Polars.select to run expressions without a context.

```ruby
foo = Polars::Series.new("foo", [1, 2, 3])
bar = Polars::Series.new("bar", [3, 2, 1])
Polars.select(min: Polars.min_horizontal(foo, bar))
```

--------------------------------

### Initialize DataFrame for Examples

Source: https://www.rubydoc.info/gems/polars-df/Polars/Expr%3Abottom_k_by

Create a sample DataFrame to demonstrate the bottom_k_by functionality.

```ruby
df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3, 4, 5, 6],
    "b" => [6, 5, 4, 3, 2, 1],
    "c" => ["Apple", "Orange", "Apple", "Apple", "Banana", "Banana"],
  }
)
```

--------------------------------

### Pad string start

Source: https://www.rubydoc.info/gems/polars-df/Polars/StringExpr

Pads the start of a string until it reaches the specified length using a fill character.

```ruby
df = Polars::DataFrame.new({"a": ["cow", "monkey", "hippopotamus", nil]})
df.with_columns(padded: Polars.col("a").str.pad_start(8, "*"))
```

```ruby
# File 'lib/polars/string_expr.rb', line 677

def pad_start(length, fill_char = " ")
  length = Utils.parse_into_expression(length)
  Utils.wrap_expr(_rbexpr.str_pad_start(length, fill_char))
end
```

--------------------------------

### starts_with(prefix)

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryNameSpace

Check if values start with a binary substring.

```APIDOC
## starts_with(prefix)

### Description
Check if values start with a binary substring.

### Parameters
- **prefix** (String) - Required - Prefix substring.

### Returns
- **Series** - A Series of booleans indicating if the condition is met.
```

--------------------------------

### starts_with(prefix)

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryExpr

Checks if binary values start with a specified prefix substring.

```APIDOC
## starts_with(prefix)

### Description
Check if values start with a binary substring.

### Parameters
- **prefix** (String) - Required - Prefix substring to check against.

### Returns
- **Expr** - A boolean expression indicating if the binary value starts with the prefix.
```

--------------------------------

### starts_with

Source: https://www.rubydoc.info/gems/polars-df/Polars/CatExpr

Checks if the string representations of values start with a specified prefix.

```APIDOC
## starts_with(prefix)

### Description
Checks if string representations of values start with a substring. Requires a literal string value.

### Parameters
- **prefix** (String) - Required - The prefix substring to check for.

### Returns
- **Expr** - The resulting expression.
```

--------------------------------

### starts_with(prefix)

Source: https://www.rubydoc.info/gems/polars-df/Polars/StringExpr

Check if string values start with a substring.

```APIDOC
## starts_with(prefix)

### Description
Check if string values start with a substring.

### Parameters
- **prefix** (String) - Required - Prefix substring.

### Returns
- **Expr**
```

--------------------------------

### Binning Series with qcut

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Examples demonstrating how to divide a Series into categories using predefined probabilities or uniform bin counts.

```ruby
s = Polars::Series.new("foo", [-2, -1, 0, 1, 2])
s.qcut([0.25, 0.75], labels: ["a", "b", "c"])
# =>
# shape: (5,)
# Series: 'foo' [cat]
# [
#         "a"
#         "a"
#         "b"
#         "b"
#         "c"
# ]
```

```ruby
s.qcut(2, labels: ["low", "high"], left_closed: true)
# =>
# shape: (5,)
# Series: 'foo' [cat]
# [
#         "low"
#         "low"
#         "high"
#         "high"
#         "high"
# ]
```

```ruby
cut = s.qcut([0.25, 0.75], include_breaks: true).alias("cut")
s.to_frame.with_columns(cut).unnest("cut")
# =>
# shape: (5, 3)
# ┌─────┬─────────────┬────────────┐
# │ foo ┆ break_point ┆ category   │
# │ --- ┆ ---         ┆ ---        │
# │ i64 ┆ f64         ┆ cat        │
# ╞═════╪═════════════╪════════════╡
# │ -2  ┆ -1.0        ┆ (-inf, -1] │
# │ -1  ┆ -1.0        ┆ (-inf, -1] │
# │ 0   ┆ 1.0         ┆ (-1, 1]    │
# │ 1   ┆ 1.0         ┆ (-1, 1]    │
# │ 2   ┆ inf         ┆ (1, inf]   │
# └─────┴─────────────┴────────────┘
```

--------------------------------

### Retrieve lower bound of a Series

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series%3Alower_bound

Examples showing how to get the lower bound for different data types.

```ruby
s = Polars::Series.new("s", [-1, 0, 1], dtype: Polars::Int32)
s.lower_bound
# =>
# shape: (1,)
# Series: 's' [i32]
# [
#         -2147483648
# ]
```

```ruby
s = Polars::Series.new("s", [1.0, 2.5, 3.0], dtype: Polars::Float32)
s.lower_bound
# =>
# shape: (1,)
# Series: 's' [f32]
# [
#         -inf
# ]
```

--------------------------------

### Generate a time range with Polars

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions%3Atime_range

Example of generating a time range with a specific start time and interval, returning a Series.

```ruby
Polars.time_range(
  Time.utc(2000, 1, 1, 14, 0),
  nil,
  "3h15m",
  eager: true
).alias("time")
```

--------------------------------

### Polars::Catalog#initialize

Source: https://www.rubydoc.info/gems/polars-df/Polars/Catalog%3Ainitialize

Initializes a new catalog client instance with the specified workspace URL and authentication settings.

```APIDOC
## initialize(workspace_url, bearer_token: "auto", require_https: true)

### Description
Initializes a catalog client. Note that this functionality is considered unstable and may change at any point.

### Parameters
- **workspace_url** (String) - Required - URL of the workspace, or alternatively the URL of the Unity catalog API endpoint.
- **bearer_token** (String) - Optional (default: "auto") - Bearer token to authenticate with. Can be set to "auto" to retrieve from environment or "databricks-sdk" to use the Databricks SDK.
- **require_https** (Boolean) - Optional (default: true) - Require the workspace_url to use HTTPS.

### Returns
- **Catalog** - A new instance of the Catalog client.
```

--------------------------------

### initialize(workspace_url, bearer_token: "auto", require_https: true)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Catalog

Initializes a new catalog client instance. This functionality is considered unstable.

```APIDOC
## initialize(workspace_url, bearer_token: "auto", require_https: true)

### Description
Initializes a catalog client. This functionality is considered unstable and may change without notice.

### Parameters
- **workspace_url** (String) - Required - URL of the workspace, or alternatively the URL of the Unity catalog API endpoint.
- **bearer_token** (String) - Optional (default: "auto") - Bearer token to authenticate with. Can be "auto" to retrieve from environment or "databricks-sdk" to use the Databricks SDK.
- **require_https** (Boolean) - Optional (default: true) - Require the workspace_url to use HTTPS.
```

--------------------------------

### Cumulative Fold Example

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions%3Acum_fold

Demonstrates using cum_fold to sum values across columns 'a', 'b', and 'c' starting with an initial value of 1.

```ruby
df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => [3, 4, 5],
    "c" => [5, 6, 7]
  }
)
df.with_columns(
  Polars.cum_fold(Polars.lit(1), Polars.all) { |acc, x| acc + x }
)
```

--------------------------------

### Check boolean Series with all?

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series%3Aall%3F

Examples demonstrating the behavior of all? on different boolean Series inputs.

```ruby
Polars::Series.new([true, true]).all?
# => true
```

```ruby
Polars::Series.new([false, true]).all?
# => false
```

```ruby
Polars::Series.new([nil, true]).all?
# => true
```

--------------------------------

### Polars::Expr#slice(offset, length = nil)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Expr%3Aslice

Get a slice of this expression. Negative indexing is supported for the offset. If length is nil, all rows starting at the offset are selected.

```APIDOC
## Polars::Expr#slice

### Description
Get a slice of this expression. Negative indexing is supported for the offset.

### Parameters
- **offset** (Integer) - Required - Start index. Negative indexing is supported.
- **length** (Integer) - Optional - Length of the slice. If set to nil, all rows starting at the offset will be selected.

### Returns
- **Expr** - The sliced expression.

### Example
```ruby
df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10, 11],
    "b" => [nil, 4, 4, 4]
  }
)
df.select(Polars.all.slice(1, 2))
```
```

--------------------------------

### Initialize DataFrame for indexing

Source: https://www.rubydoc.info/gems/polars-df/Polars/DataFrame%3A%5B%5D

Create a sample DataFrame to demonstrate various indexing operations.

```ruby
df = Polars::DataFrame.new(
  {"a" => [1, 2, 3], "d" => [4, 5, 6], "c" => [1, 3, 2], "b" => [7, 8, 9]}
)
```

--------------------------------

### Execute SQL to show tables

Source: https://www.rubydoc.info/gems/polars-df/Polars/SQLContext%3Atables

Demonstrates registering a DataFrame in a SQLContext and querying the table list using SQL.

```ruby
frame_data = Polars::DataFrame.new({"hello" => ["world"]})
ctx = Polars::SQLContext.new(hello_world: frame_data)
ctx.execute("SHOW TABLES", eager: true)
# =>
# shape: (1, 1)
# ┌─────────────┐
# │ name        │
# │ ---         │
# │ str         │
# ╞═════════════╡
# │ hello_world │
# └─────────────┘
```

--------------------------------

### Implementation of get method

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryExpr%3Aget

The internal implementation of the get method in the Polars library.

```ruby
def get(index, null_on_oob: false)
  index_rbexpr = Utils.parse_into_expression(index)
  Utils.wrap_expr(_rbexpr.bin_get(index_rbexpr, null_on_oob))
end
```

--------------------------------

### Series#initialize

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Creates a new Series instance.

```APIDOC
## Series#initialize(name = nil, values = nil, dtype: nil, strict: true, nan_to_null: false)

### Description
Create a new Series.

### Parameters
- **name** (String) - Optional - Name of the series.
- **values** (Array) - Optional - Initial values.
- **dtype** (Symbol) - Optional - Data type.
- **strict** (Boolean) - Optional - Whether to enforce strict typing.
- **nan_to_null** (Boolean) - Optional - Whether to convert NaN to null.
```

--------------------------------

### Implementation of ArrayExpr#get

Source: https://www.rubydoc.info/gems/polars-df/Polars/ArrayExpr%3Aget

The internal implementation of the get method in the Polars library.

```ruby
def get(index, null_on_oob: false)
  index = Utils.parse_into_expression(index)
  Utils.wrap_expr(_rbexpr.arr_get(index, null_on_oob))
end
```

--------------------------------

### Initialize DataFrame for Time Selection

Source: https://www.rubydoc.info/gems/polars-df/Polars/Selectors.time

Sets up a DataFrame with datetime, date, and time columns to demonstrate selector functionality.

```ruby
df = Polars::DataFrame.new(
  {
    "dtm" => [DateTime.new(2001, 5, 7, 10, 25), DateTime.new(2031, 12, 31, 0, 30)],
    "dt" => [Date.new(1999, 12, 31), Date.new(2024, 8, 9)],
    "tm" => [Time.utc(2001, 1, 1, 0, 0, 0), Time.utc(2001, 1, 1, 23, 59, 59)]
  },
  schema_overrides: {"tm" => Polars::Time}
)
```

--------------------------------

### pad_start(length, fill_char = " ")

Source: https://www.rubydoc.info/gems/polars-df/Polars/StringExpr

Pad the start of the string until it reaches the given length.

```APIDOC
## pad_start(length, fill_char = " ")

### Description
Pad the start of the string until it reaches the given length. Strings with length equal to or greater than this value are returned as-is.

### Parameters
- **length** (Integer) - Required - Pad the string until it reaches this length.
- **fill_char** (String) - Optional (default: " ") - The character to pad the string with.

### Returns
- **Expr** - The resulting expression.
```

--------------------------------

### Implementation of the get method

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryNameSpace%3Aget

The source code definition for the get method within the BinaryNameSpace class.

```ruby
def get(index, null_on_oob: false)
  super
end
```

--------------------------------

### Polars::SQLContext#initialize

Source: https://www.rubydoc.info/gems/polars-df/Polars/SQLContext

Initializes a new SQLContext instance.

```APIDOC
## SQLContext#initialize

### Description
Initializes a new SQLContext instance to manage SQL queries against registered frames.

### Parameters
- **frames** (Hash) - Optional - A hash of names to frames.
- **register_globals** (Boolean) - Optional - Whether to register global frames.
- **eager** (Boolean) - Optional - Whether to default to eager execution.
- **named_frames** (Hash) - Optional - Additional frames passed as keyword arguments.
```

--------------------------------

### Initialize QueryOptFlags

Source: https://www.rubydoc.info/gems/polars-df/Polars/QueryOptFlags%3Ainitialize

Creates a new QueryOptFlags instance by setting default optimization flags and applying provided overrides.

```ruby
def initialize(
  predicate_pushdown: nil,
  projection_pushdown: nil,
  simplify_expression: nil,
  slice_pushdown: nil,
  comm_subplan_elim: nil,
  comm_subexpr_elim: nil,
  cluster_with_columns: nil,
  collapse_joins: nil,
  check_order_observe: nil,
  fast_projection: nil,
  sort_collapse: nil
)
  self._rboptflags = RbOptFlags.default
  update(
    predicate_pushdown: predicate_pushdown,
    projection_pushdown: projection_pushdown,
    simplify_expression: simplify_expression,
    slice_pushdown: slice_pushdown,
    comm_subplan_elim: comm_subplan_elim,
    comm_subexpr_elim: comm_subexpr_elim,
    cluster_with_columns: cluster_with_columns,
    collapse_joins: collapse_joins,
    check_order_observe: check_order_observe,
    fast_projection: fast_projection,
    sort_collapse: sort_collapse
  )
end
```

--------------------------------

### Source code for Polars::ArrayNameSpace#get

Source: https://www.rubydoc.info/gems/polars-df/Polars/ArrayNameSpace%3Aget

The implementation of the get method within the Polars library.

```ruby
# File 'lib/polars/array_name_space.rb', line 532

def get(index, null_on_oob: false)
  super
end
```

--------------------------------

### sample

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListNameSpace

Sample from this list.

```APIDOC
## sample

### Description
Sample from this list.

### Parameters
- **n** (Integer) - Optional - Number of items to return. Cannot be used with fraction.
- **fraction** (Float) - Optional - Fraction of items to return. Cannot be used with n.
- **with_replacement** (Boolean) - Optional - Allow values to be sampled more than once.
- **shuffle** (Boolean) - Optional - Shuffle the order of sampled data points.
- **seed** (Integer) - Optional - Seed for the random number generator.

### Returns
- **Series**
```

--------------------------------

### Sample from list

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListNameSpace

Samples items from the list based on provided parameters like n or fraction.

```ruby
s = Polars::Series.new("values", [[1, 2, 3], [4, 5]])
s.list.sample(n: Polars::Series.new("n", [2, 1]), seed: 1)
```

```ruby
# File 'lib/polars/list_name_space.rb', line 143

def sample(n: nil, fraction: nil, with_replacement: false, shuffle: false, seed: nil)
  super
end
```

--------------------------------

### get(index, null_on_oob: false)

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryNameSpace

Get the byte value at the given index for every binary value in the Series.

```APIDOC
## get(index, null_on_oob: false)

### Description
Get the byte value at the given index. Index 0 returns the first byte, and -1 returns the last byte.

### Parameters
- **index** (Object) - Required - Index to return per binary value.
- **null_on_oob** (Boolean) - Optional (default: false) - Behavior if index is out of bounds: true sets as null, false raises an error.

### Returns
- **Series** - A Series containing the retrieved bytes.
```

--------------------------------

### Demonstrating Series chunking behavior

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series%3Arechunk

Examples showing how to check the number of chunks in a Series and how rechunk consolidates them.

```ruby
s1 = Polars::Series.new("a", [1, 2, 3])
s1.n_chunks
# => 1
```

```ruby
s2 = Polars::Series.new("a", [4, 5, 6])
s = Polars.concat([s1, s2], rechunk: false)
s.n_chunks
# => 2
```

```ruby
s.rechunk(in_place: true)
# =>
# shape: (6,)
# Series: 'a' [i64]
# [
#         1
#         2
#         3
#         4
#         5
#         6
# ]
```

```ruby
s.n_chunks
# => 1
```

--------------------------------

### Check if Categorical starts with a prefix

Source: https://www.rubydoc.info/gems/polars-df/Polars/CatNameSpace

Checks if the string representation of each value in a Categorical Series starts with the specified prefix.

```ruby
s = Polars::Series.new("fruits", ["apple", "mango", nil], dtype: Polars::Categorical)
s.cat.starts_with("app")
# =>
# shape: (3,)
# Series: 'fruits' [bool]
# [
#         true
#         false
#         null
# ]
```

```ruby
# File 'lib/polars/cat_name_space.rb', line 124

def starts_with(prefix)
  super
end
```

--------------------------------

### Check binary prefix with starts_with

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryNameSpace%3Astarts_with

Demonstrates checking if elements in a binary series start with a specific byte sequence.

```ruby
s = Polars::Series.new("colors", ["\x00\x00\x00".b, "\xff\xff\x00".b, "\x00\x00\xff".b])
s.bin.starts_with("\x00".b)
# =>
# shape: (3,)
# Series: 'colors' [bool]
# [
#         true
#         false
#         true
# ]
```

--------------------------------

### get(index, null_on_oob: false)

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListExpr

Get the value by index in the sublists. If an index is out of bounds, it returns nil or raises an error based on the null_on_oob parameter.

```APIDOC
## get(index, null_on_oob: false)

### Description
Get the value by index in the sublists. Index 0 returns the first item, -1 returns the last item.

### Parameters
- **index** (Integer) - Required - Index to return per sublist.
- **null_on_oob** (Boolean) - Optional (default: false) - Behavior if an index is out of bounds: true sets as null, false raises an error.

### Returns
- **Expr** - The resulting expression.
```

--------------------------------

### Retrieve values from sub-arrays using ArrayExpr#get

Source: https://www.rubydoc.info/gems/polars-df/Polars/ArrayExpr%3Aget

Demonstrates using the get method to extract elements from an array column based on an index column, with null_on_oob enabled to handle out-of-bounds indices.

```ruby
df = Polars::DataFrame.new(
  {"arr" => [[1, 2, 3], [4, 5, 6], [7, 8, 9]], "idx" => [1, -2, 4]},
  schema: {"arr" => Polars::Array.new(Polars::Int32, 3), "idx" => Polars::Int32}
)
df.with_columns(get: Polars.col("arr").arr.get("idx", null_on_oob: true))
```

--------------------------------

### BinaryNameSpace#starts_with implementation

Source: https://www.rubydoc.info/gems/polars-df/Polars/BinaryNameSpace%3Astarts_with

The source code definition for the starts_with method within the binary namespace.

```ruby
def starts_with(prefix)
  super
end
```

--------------------------------

### Polars.linear_spaces(start, stop, num_samples, closed: "both", as_array: false, eager: false)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions%3Alinear_spaces

Generates a sequence of evenly-spaced values for each row between start and end. The number of values in each sequence is determined by num_samples.

```APIDOC
## Polars.linear_spaces

### Description
Generates a sequence of evenly-spaced values for each row between `start` and `end`. The number of values in each sequence is determined by `num_samples`.

### Parameters
- **start** (Object) - Required - Lower bound of the range.
- **stop** (Object) - Required - Upper bound of the range.
- **num_samples** (Integer) - Required - Number of samples in the output sequence.
- **closed** ('both', 'left', 'right', 'none') - Optional (default: "both") - Define which sides of the interval are closed (inclusive).
- **as_array** (Boolean) - Optional (default: false) - Return result as a fixed-length Array. num_samples must be a constant.
- **eager** (Boolean) - Optional (default: false) - Evaluate immediately and return a Series. If set to false, return an expression instead.

### Returns
- **Expr, Series** - Returns an expression or a Series depending on the eager parameter.
```

--------------------------------

### Implementation of starts_with

Source: https://www.rubydoc.info/gems/polars-df/Polars/CatExpr%3Astarts_with

The source code implementation for the starts_with method, enforcing a string type check on the prefix.

```ruby
def starts_with(prefix)
  if !prefix.is_a?(::String)
    msg = "'prefix' must be a string; found #{prefix.inspect}"
    raise TypeError, msg
  end
  Utils.wrap_expr(_rbexpr.cat_starts_with(prefix))
end
```

--------------------------------

### Select columns and expressions in Polars

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Aselect

Examples demonstrating column selection, expression arithmetic, and conditional logic using select.

```ruby
df = Polars::DataFrame.new(
  {
    "foo" => [1, 2, 3],
    "bar" => [6, 7, 8],
    "ham" => ["a", "b", "c"],
  }
).lazy
df.select("foo").collect
```

```ruby
df.select(["foo", "bar"]).collect
```

```ruby
df.select(Polars.col("foo") + 1).collect
```

```ruby
df.select([Polars.col("foo") + 1, Polars.col("bar") + 1]).collect
```

```ruby
df.select(Polars.when(Polars.col("foo") > 2).then(10).otherwise(0)).collect
```

--------------------------------

### Polars.business_day_count(start, stop, week_mask: [true, true, true, true, true, false, false], holidays: [])

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions%3Abusiness_day_count

Calculates the number of business days between start and stop dates. Note: This functionality is considered unstable.

```APIDOC
## Polars.business_day_count

### Description
Counts the number of business days between `start` and `stop` (not including `stop`).

### Parameters
- **start** (Object) - Required - Start dates.
- **stop** (Object) - Required - End dates.
- **week_mask** (Array) - Optional - Which days of the week to count. Defaults to [true, true, true, true, true, false, false] (Monday to Friday).
- **holidays** (Array) - Optional - Holidays to exclude from the count. Defaults to [].

### Returns
- **Expr** - A Polars expression representing the business day count.
```

--------------------------------

### Rolling Aggregation Example

Source: https://www.rubydoc.info/gems/polars-df/Polars/Expr%3Arolling

Demonstrates applying rolling sum, min, and max aggregations over a 2-day window on a datetime column.

```ruby
dates = [
  "2020-01-01 13:45:48",
  "2020-01-01 16:42:13",
  "2020-01-01 16:45:09",
  "2020-01-02 18:12:48",
  "2020-01-03 19:45:32",
  "2020-01-08 23:16:43"
]
df = Polars::DataFrame.new({"dt" => dates, "a": [3, 7, 5, 9, 2, 1]}).with_columns(
  Polars.col("dt").str.strptime(Polars::Datetime).set_sorted
)
df.with_columns(
  sum_a: Polars.sum("a").rolling(index_column: "dt", period: "2d"),
  min_a: Polars.min("a").rolling(index_column: "dt", period: "2d"),
  max_a: Polars.max("a").rolling(index_column: "dt", period: "2d")
)
```

--------------------------------

### slice

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get a slice of this Series.

```APIDOC
## slice(offset, length = nil)

### Description
Get a slice of this Series.

### Parameters
- **offset** (Integer) - Required - Start index. Negative indexing is supported.
- **length** (Integer, nil) - Optional - Length of the slice. If set to nil, all rows starting at the offset will be selected. Defaults to nil.

### Returns
- **Series** - The sliced Series.
```

--------------------------------

### Performing Joins on LazyFrames

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Ajoin

Examples demonstrating various join strategies including inner, full, left, semi, and anti joins.

```ruby
df = Polars::DataFrame.new(
  {
    "foo" => [1, 2, 3],
    "bar" => [6.0, 7.0, 8.0],
    "ham" => ["a", "b", "c"]
  }
).lazy
other_df = Polars::DataFrame.new(
  {
    "apple" => ["x", "y", "z"],
    "ham" => ["a", "b", "d"]
  }
).lazy
df.join(other_df, on: "ham").collect
```

```ruby
df.join(other_df, on: "ham", how: "full").collect
```

```ruby
df.join(other_df, on: "ham", how: "left").collect
```

```ruby
df.join(other_df, on: "ham", how: "semi").collect
```

```ruby
df.join(other_df, on: "ham", how: "anti").collect
```

--------------------------------

### name

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the name of this Series.

```APIDOC
## name

### Description
Get the name of this Series.

### Returns
- String
```

--------------------------------

### Retrieve Schema Column Names

Source: https://www.rubydoc.info/gems/polars-df/Polars/Schema%3Anames

Demonstrates how to initialize a schema and extract its column names as an array.

```ruby
s = Polars::Schema.new({"x" => Polars::Float64.new, "y" => Polars::Datetime.new(time_zone: "UTC")})
s.names
# => ["x", "y"]
```

--------------------------------

### median

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the median of this Series.

```APIDOC
## median

### Description
Get the median of this Series.

### Returns
- Float or nil
```

--------------------------------

### to_dummies

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get dummy variables from the Series.

```APIDOC
## to_dummies

### Description
Get dummy variables.

### Parameters
- **separator** (String) - Optional - Separator/delimiter used when generating column names. Defaults to "_".
- **drop_first** (Boolean) - Optional - Remove the first category from the variable being encoded. Defaults to false.
- **drop_nulls** (Boolean) - Optional - If there are nil values in the series, a null column is not generated. Defaults to false.

### Returns
- **DataFrame**
```

--------------------------------

### sample(n: nil, fraction: nil, with_replacement: false, shuffle: false, seed: nil)

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListExpr

Samples items from a list expression. You can specify either the number of items (n) or a fraction of the total items.

```APIDOC
## sample(n: nil, fraction: nil, with_replacement: false, shuffle: false, seed: nil)

### Description
Sample from this list expression.

### Parameters
- **n** (Integer) - Optional - Number of items to return. Cannot be used with fraction.
- **fraction** (Float) - Optional - Fraction of items to return. Cannot be used with n.
- **with_replacement** (Boolean) - Optional - Allow values to be sampled more than once. Defaults to false.
- **shuffle** (Boolean) - Optional - Shuffle the order of sampled data points. Defaults to false.
- **seed** (Integer) - Optional - Seed for the random number generator.

### Returns
- **Expr** - The resulting expression.
```

--------------------------------

### min

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the minimal value in this Series.

```APIDOC
## min

### Description
Get the minimal value in this Series.

### Returns
- Object
```

--------------------------------

### last

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the last element of the Series.

```APIDOC
## last

### Description
Get the last element of the Series. Returns nil if the Series is empty.

### Parameters
- **ignore_nulls** (Boolean) - Optional - Ignore null values (default: false).

### Returns
- **Object**
```

--------------------------------

### sample(n: nil, fraction: nil, with_replacement: false, shuffle: false, seed: nil)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Samples elements from the Series.

```APIDOC
## sample(n: nil, fraction: nil, with_replacement: false, shuffle: false, seed: nil)

### Description
Sample from this Series.

### Parameters
- **n** (Integer, optional) - Optional - Number of items to sample.
- **fraction** (Float, optional) - Optional - Fraction of items to sample.
- **with_replacement** (Boolean, optional) - Optional - Whether to sample with replacement.
- **shuffle** (Boolean, optional) - Optional - Whether to shuffle the result.
- **seed** (Integer, optional) - Optional - Random seed.
```

--------------------------------

### Get Schema Length

Source: https://www.rubydoc.info/gems/polars-df/Polars/Schema%3Alength

Demonstrates how to initialize a schema and retrieve the number of entries it contains.

```ruby
s = Polars::Schema.new({"x" => Polars::Int32.new, "y" => Polars::List.new(Polars::String)})
s.length
# => 2
```

--------------------------------

### is_unique

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get mask of all unique values.

```APIDOC
## is_unique

### Description
Get mask of all unique values.

### Returns
- **Series**
```

--------------------------------

### flags

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get flags that are set on the Series.

```APIDOC
## flags

### Description
Get flags that are set on the Series, such as sorting status or fast explode capability.

### Returns
- (Hash) A hash containing the flag names and their boolean values.
```

--------------------------------

### Method implementation

Source: https://www.rubydoc.info/gems/polars-df/Polars/DateTimeExpr%3Aminute

The source code implementation of the minute method.

```ruby
# File 'lib/polars/date_time_expr.rb', line 1098

def minute
  Utils.wrap_expr(_rbexpr.dt_minute)
end
```

--------------------------------

### arg_unique

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get unique index as Series.

```APIDOC
## Series#arg_unique

### Description
Get unique index as Series.

### Returns
- **Series**
```

--------------------------------

### max

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the maximum value in the Series.

```APIDOC
## Series#max

### Description
Returns the maximum value found in the Series.

### Returns
- **Object**
```

--------------------------------

### fields

Source: https://www.rubydoc.info/gems/polars-df/Polars/StructNameSpace

Get the names of the fields in the struct.

```APIDOC
## fields()

### Description
Get the names of the fields.

### Returns
- **Array** - A list of field names.
```

--------------------------------

### len()

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListNameSpace

Get the length of the arrays as UInt32.

```APIDOC
## len()

### Description
Get the length of the arrays as UInt32.

### Returns
- **Series** - The resulting Series.
```

--------------------------------

### Rolling Datetimes to Month Start

Source: https://www.rubydoc.info/gems/polars-df/Polars/DateTimeNameSpace%3Amonth_start

Demonstrates using month_start to adjust a range of datetimes to the first day of each month.

```ruby
s = Polars.datetime_range(
  DateTime.new(2000, 1, 2, 2), DateTime.new(2000, 4, 2, 2), "1mo", time_unit: "us", eager: true
).alias("datetime")
s.dt.month_start
# =>
# shape: (4,)
# Series: 'datetime' [datetime[μs]]
# [
#         2000-01-01 02:00:00
#         2000-02-01 02:00:00
#         2000-03-01 02:00:00
#         2000-04-01 02:00:00
# ]
```

--------------------------------

### first()

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListExpr

Get the first value of the sublists.

```APIDOC
## first()

### Description
Get the first value of the sublists.

### Returns
- (Expr)
```

--------------------------------

### Clear DataFrame Examples

Source: https://www.rubydoc.info/gems/polars-df/Polars/DataFrame%3Aclear

Demonstrates creating an empty DataFrame and a DataFrame with a specified number of null rows.

```ruby
df = Polars::DataFrame.new(
  {
    "a" => [nil, 2, 3, 4],
    "b" => [0.5, nil, 2.5, 13],
    "c" => [true, true, false, nil]
  }
)
df.clear
# =>
# shape: (0, 3)
# ┌─────┬─────┬──────┐
# │ a   ┆ b   ┆ c    │
# │ --- ┆ --- ┆ ---  │
# │ i64 ┆ f64 ┆ bool │
# ╞═════╪═════╪══════╡
# └─────┴─────┴──────┘
```

```ruby
df.clear(2)
# =>
# shape: (2, 3)
# ┌──────┬──────┬──────┐
# │ a    ┆ b    ┆ c    │
# │ ---  ┆ ---  ┆ ---  │
# │ i64  ┆ f64  ┆ bool │
# ╞══════╪══════╪══════╡
# │ null ┆ null ┆ null │
# │ null ┆ null ┆ null │
# └──────┴──────┴──────┘
```

--------------------------------

### first()

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListNameSpace

Get the first value of the sublists.

```APIDOC
## first()

### Description
Get the first value of the sublists.

### Returns
- **Series** - A Series containing the first elements.
```

--------------------------------

### Visualize a LazyFrame query plan

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Ashow_graph

Demonstrates how to chain operations on a LazyFrame and visualize the resulting query plan using show_graph.

```ruby
lf = Polars::LazyFrame.new(
  {
    "a" => ["a", "b", "a", "b", "b", "c"],
    "b" => [1, 2, 3, 4, 5, 6],
    "c" => [6, 5, 4, 3, 2, 1]
  }
)
lf.group_by("a", maintain_order: true).agg(Polars.all.sum).sort(
  "a"
).show_graph
```

--------------------------------

### Rolling aggregation example

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Arolling

Demonstrates how to perform a rolling aggregation on a datetime column with a 2-day window.

```ruby
dates = [
  "2020-01-01 13:45:48",
  "2020-01-01 16:42:13",
  "2020-01-01 16:45:09",
  "2020-01-02 18:12:48",
  "2020-01-03 19:45:32",
  "2020-01-08 23:16:43"
]
df = Polars::LazyFrame.new({"dt" => dates, "a" => [3, 7, 5, 9, 2, 1]}).with_columns(
  Polars.col("dt").str.strptime(Polars::Datetime).set_sorted
)
df.rolling(index_column: "dt", period: "2d").agg(
  [
    Polars.sum("a").alias("sum_a"),
    Polars.min("a").alias("min_a"),
    Polars.max("a").alias("max_a")
  ]
).collect
```

--------------------------------

### [](item)

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListNameSpace

Get the value by index in the sublists.

```APIDOC
## [](item)

### Description
Get the value by index in the sublists.

### Parameters
- **item** (Object) - Required - The index to retrieve from the sublists.

### Returns
- **Series** - The resulting Series.
```

--------------------------------

### Initialize Polars Catalog Client

Source: https://www.rubydoc.info/gems/polars-df/Polars/Catalog%3Ainitialize

Initializes a new catalog client instance. Note that this functionality is currently marked as unstable.

```ruby
def initialize(workspace_url, bearer_token: "auto", require_https: true)
  if require_https && !workspace_url.start_with?("https://")
    msg = (
      "a non-HTTPS workspace_url was given. To " +
      "allow non-HTTPS URLs, pass require_https: false."
    )
    raise ArgumentError, msg
  end

  if bearer_token == "auto"
    bearer_token = nil
  end

  @client = RbCatalogClient.new(workspace_url, bearer_token)
end
```

--------------------------------

### [](item)

Source: https://www.rubydoc.info/gems/polars-df/Polars/ListExpr

Get the value by index in the sublists.

```APIDOC
## [](item)

### Description
Get the value by index in the sublists.

### Parameters
- **item** (Object) - Required - The index to retrieve.

### Returns
- **Expr** - The expression representing the indexed value.
```

--------------------------------

### Initialize DataFrame for Polars::Functions#exclude

Source: https://www.rubydoc.info/gems/polars-df/Polars/Functions%3Aexclude

Setup a sample DataFrame to demonstrate column exclusion.

```ruby
df = Polars::DataFrame.new(
  {
    "aa" => [1, 2, 3],
    "ba" => ["a", "b", nil],
    "cc" => [nil, 2.5, 1.5]
  }
)
```

--------------------------------

### last

Source: https://www.rubydoc.info/gems/polars-df/Polars/ArrayExpr

Get the last value of the sub-arrays.

```APIDOC
## last

### Description
Returns the last value of each sub-array in the column.

### Returns
- **Expr** - A Polars expression representing the last element of each array.
```

--------------------------------

### get

Source: https://www.rubydoc.info/gems/polars-df/Polars/ArrayExpr

Retrieves a value by index from sub-arrays.

```APIDOC
## get(index, null_on_oob: false)

### Description
Get the value by index in the sub-arrays. Index 0 returns the first item, and negative indices return items from the end.

### Parameters
- **index** (Integer) - Required - Index to return per sub-array.
- **null_on_oob** (Boolean) - Optional (default: false) - Behavior if an index is out of bounds: true sets as null, false raises an error.

### Returns
- **Expr** - The resulting expression.
```

--------------------------------

### Implementation of the profile method

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Aprofile

The internal implementation of the profile method, showing how it handles engine selection and optimization flags.

```ruby
def profile(
  engine: "auto",
  optimizations: DEFAULT_QUERY_OPT_FLAGS
)
  engine = _select_engine(engine)

  ldf = _ldf.with_optimizations(optimizations._rboptflags)

  df_rb, timings_rb = ldf.profile
  [Utils.wrap_df(df_rb), Utils.wrap_df(timings_rb)]
end
```

--------------------------------

### n_chunks

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the number of chunks that this Series contains.

```APIDOC
## n_chunks

### Description
Get the number of chunks that this Series contains.

### Returns
- Integer
```

--------------------------------

### Implementation of show_graph

Source: https://www.rubydoc.info/gems/polars-df/Polars/LazyFrame%3Ashow_graph

The source code implementation of the show_graph method, showing how it handles engine selection, plan stages, and dot graph generation.

```ruby
def show_graph(
  optimized: true,
  show: true,
  output_path: nil,
  raw_output: false,
  figsize: [16.0, 12.0],
  engine: "auto",
  plan_stage: "ir",
  optimizations: DEFAULT_QUERY_OPT_FLAGS
)
  engine = _select_engine(engine)

  if engine == "streaming"
    issue_unstable_warning("streaming mode is considered unstable.")
  end

  optimizations = optimizations.dup
  optimizations._rboptflags.streaming = engine == "streaming"
  _ldf = self._ldf.with_optimizations(optimizations._rboptflags)

  if plan_stage == "ir"
    dot = _ldf.to_dot(optimized)
  elsif plan_stage == "physical"
    if engine == "streaming"
      dot = _ldf.to_dot_streaming_phys(optimized)
    else
      dot = _ldf.to_dot(optimized)
    end
  else
    error_msg = "invalid plan stage '#{plan_stage}'"
    raise TypeError, error_msg
  end

  Utils.display_dot_graph(
    dot: dot,
    show: show,
    output_path: output_path,
    raw_output: raw_output
  )
end
```

--------------------------------

### limit

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the first n rows of the Series.

```APIDOC
## limit(n = 10)

### Description
Get the first n rows. Alias for #head.

### Parameters
- **n** (Integer) - Optional - Number of rows to return. Defaults to 10.

### Returns
- **Series** - A new Series containing the first n rows.
```

--------------------------------

### Retrieve DataFrame Schema

Source: https://www.rubydoc.info/gems/polars-df/Polars/DataFrame%3Aschema

Demonstrates how to initialize a DataFrame and retrieve its schema definition.

```ruby
df = Polars::DataFrame.new(
  {
    "foo" => [1, 2, 3],
    "bar" => [6.0, 7.0, 8.0],
    "ham" => ["a", "b", "c"]
  }
)
df.schema
# => Polars::Schema({"foo"=>Polars::Int64, "bar"=>Polars::Float64, "ham"=>Polars::String})
```

--------------------------------

### is_first_distinct()

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get a mask of the first unique value.

```APIDOC
## is_first_distinct()

### Description
Get a mask of the first unique value.

### Returns
- (Series)
```

--------------------------------

### create_catalog(catalog_name, comment: nil, storage_root: nil)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Catalog

Creates a new catalog in the Unity Catalog. This functionality is considered unstable.

```APIDOC
## create_catalog(catalog_name, comment: nil, storage_root: nil)

### Description
Create a catalog. This functionality is considered unstable.

### Parameters
- **catalog_name** (String) - Required - Name of the catalog.
- **comment** (String) - Optional - Leaves a comment about the catalog.
- **storage_root** (String) - Optional - Base location at which to store the catalog.

### Returns
- **CatalogInfo**
```

--------------------------------

### get_chunks

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the chunks of this Series as a list of Series.

```APIDOC
## get_chunks

### Description
Get the chunks of this Series as a list of Series.

### Returns
- (Array) An array of Series objects.
```

--------------------------------

### std(ddof: 1)

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Get the standard deviation of this Series.

```APIDOC
## std(ddof: 1)

### Description
Get the standard deviation of this Series.

### Parameters
- **ddof** (Integer) - Optional - Delta Degrees of Freedom: the divisor used in the calculation is N - ddof (defaults to 1).

### Returns
- **Float, nil**
```

--------------------------------

### Get the shape of a Series

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Returns the dimensions of the Series as an array.

```ruby
s = Polars::Series.new("a", [1, 2, 3])
s.shape
# => [3]
```

```ruby
# File 'lib/polars/series.rb', line 139

def shape
  [_s.len]
end
```

--------------------------------

### Hugging Face Token Configuration

Source: https://www.rubydoc.info/gems/polars-df/Polars/IO

Example of passing an API token for Hugging Face cloud storage access.

```python
{'token': '...'}
```

--------------------------------

### Initialize eager optimization flags

Source: https://www.rubydoc.info/gems/polars-df/Polars/QueryOptFlags._eager

Creates a new QueryOptFlags instance with eager optimizations enabled and expression simplification turned on.

```ruby
def self._eager
  optflags = QueryOptFlags.new
  optflags.no_optimizations
  optflags._rboptflags.eager = true
  optflags.simplify_expression = true
  optflags
end
```

--------------------------------

### Get Series name

Source: https://www.rubydoc.info/gems/polars-df/Polars/Series

Returns the name assigned to the Series.

```ruby
s = Polars::Series.new("a", [1, 2, 3])
s.name
# => "a"
```

```ruby
# File 'lib/polars/series.rb', line 127

def name
  _s.name
end
```
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