RcppAlgos

https://jwood000.github.io/RcppAlgos/
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### partitionsSample with non-standard setup

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatorialSampling.html

Demonstrates partitionsSample with a non-standard input vector and a target sum, showing its flexibility.

```R
partitionsSample(17 + (1:10) * 3, 10, TRUE,
                 target = 320, n = 3, seed = 111)
#>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
#> [1,]   23   23   26   26   29   29   38   38   41    47
#> [2,]   26   26   26   29   29   29   32   41   41    41
#> [3,]   20   23   23   26   26   35   38   41   44    44
```

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

### Example Usage

Source: https://jwood000.github.io/RcppAlgos/reference/expandGridIterator.html

Demonstrates how to use the expandGridIter function and its methods with sample data.

```APIDOC
## Examples
```R
a = expandGridIter(factor(state.abb), euro, islands)
a@nextIter()
#>   Var1    Var2  Var3
#> 1   AL 13.7603 11506
a@nextNIter(3)
#>   Var1    Var2  Var3
#> 1   AL 13.7603  5500
#> 2   AL 13.7603 16988
#> 3   AL 13.7603  2968
a@front()
#>   Var1    Var2  Var3
#> 1   AL 13.7603 11506
all_remaining = a@nextRemaining()
dim(all_remaining)
#> [1] 26399     3
a@summary()
#> $description
#> [1] "Cartesian Product of the source (see the sourceVector method for more info)"
#> 
#> $currentIndex
#> [1] 26401
#> 
#> $totalResults
#> [1] 26400
#> 
#> $totalRemaining
#> [1] -1
#> 
a@back()
#>   Var1    Var2 Var3
#> 1   WY 200.482   82
a[[5]]
#>   Var1    Var2 Var3
#> 1   AL 13.7603   16
a@summary()
#> $description
#> [1] "Cartesian Product of the source (see the sourceVector method for more info)"
#> 
#> $currentIndex
#> [1] 5
#> 
#> $totalResults
#> [1] 26400
#> 
#> $totalRemaining
#> [1] 26395
#> 
a[[c(1, 17, 3)]]
#>   Var1    Var2  Var3
#> 1   AL 13.7603 11506
#> 2   AL 13.7603    13
#> 3   AL 13.7603 16988
a@summary()
#> $description
#> [1] "Cartesian Product of the source (see the sourceVector method for more info)"
#> 
#> $currentIndex
#> [1] 5
#> 
#> $totalResults
#> [1] 26400
#> 
#> $totalRemaining
#> [1] 26395
#> 
```
```

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

### Example of Brute-force Group Partitioning

Source: https://jwood000.github.io/RcppAlgos/articles/OtherCombinatorics.html

This example demonstrates the output of the `funBruteGrp` function, showing how a vector is partitioned into 3 groups of size 4. The output illustrates permutations within the last group.

```R
funBruteGrp(myUp = 6)
```

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

### Subset Sum with Product Constraint

Source: https://jwood000.github.io/RcppAlgos/articles/SubsetSum.html

This example demonstrates using comboGeneral with a product constraint. A helper function `getAllThenFilter` is defined to first get all combinations and then filter them, which is then compared against the optimized `comboGeneral` for performance.

```R
getAllThenFilter <- function(n, m, lim) {
    t <- comboGeneral(n, m, constraintFun = "prod")
    t[t[, m + 1] == lim, -(m+1)]
}
```

```R
library(microbenchmark)
microbenchmark(optimized = comboGeneral(25, 10, constraintFun = "prod",
                                        comparisonFun = "==",
                                        limitConstraints = 1037836800),
               brute = getAllThenFilter(25, 10, 1037836800), times = 20,
               unit = "relative", check = "equal")
```

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

### Partition Iterators and Navigation

Source: https://jwood000.github.io/RcppAlgos/reference/RcppAlgos-package.html

Shows how to initialize and navigate partition iterators. This includes starting iteration from a specific index and advancing the iterator.

```R
p_iter = partitionsIter(5000, 100, target = 6000)
p_iter[[1e9]] ## start iterating from index = 1e9
p_iter@nextIter()
p_iter@nextNIter(1e3)
```

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

### Benchmark Compositions with Repetition

Source: https://jwood000.github.io/RcppAlgos/articles/HighPerformanceBenchmarks.html

Compares RcppAlgos with 'arrangements' and 'partitions' for generating compositions with repetition. This is a small case example to illustrate the setup.

```R
t1 <- compositionsGeneral(0:15, repetition = TRUE)
t2 <- arrangements::compositions(15)
t3 <- partitions::compositions(15)

# Each package has different output formats... we only examine dimensions
```

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

### Iterating Over Partitions

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Demonstrates how to iterate over partitions of a number using partitionsIter. Shows how to get the next iteration, current iteration, and summary statistics. Random access is supported, but previous iteration is not.

```R
p = partitionsIter(16, 4)
p@nextIter()
#> [1]  1  2  3 10

p@nextIter()
#> [1] 1 2 4 9

iter = p@currIter()
i = 1

while (!is.null(iter)) {
    cat(i, " ", iter, "\n")
    iter = p@nextIter()
    i = i + 1
}
#> 1   1 2 4 9 
#> 2   1 2 5 8 
#> 3   1 2 6 7 
#> 4   1 3 4 8 
#> 5   1 3 5 7 
#> 6   1 4 5 6 
#> 7   2 3 4 7 
#> 8   2 3 5 6 
#> No more results.
```

```R
partitionsGeneral(16, 4, lower = 2)
#>      [,1] [,2] [,3] [,4]
#> [1,]    1    2    4    9
#> [2,]    1    2    5    8
#> [3,]    1    2    6    7
#> [4,]    1    3    4    8
#> [5,]    1    3    5    7
#> [6,]    1    4    5    6
#> [7,]    2    3    4    7
#> [8,]    2    3    5    6
```

```R
p@summary()
#> $description
#> [1] "Partitions of 16 into 4 parts"
#>
#> $currentIndex
#> [1] 10
#>
#> $totalResults
#> [1] 9
#>
#> $totalRemaining
#> [1] -1
```

```R
p[[7]]
#> [1] 1 4 5 6
```

```R
p@prevIter()
#> Error: no slot of name "prevIter" for this object of class "Partitions"
```

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

### Forward Iteration and Summary

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Demonstrates how to get the next combinations and retrieve summary information about the iterator's state.

```APIDOC
## Get the remaining combinations with nextRemaining
a$nextRemaining()
#>      [,1] [,2] [,3]
#> [1,]    1    3    5
#> [2,]    1    4    5
#> [3,]    2    3    4
#> [4,]    2    3    5
#> [5,]    2    4    5
#> [6,]    3    4    5

a$summary()
#> $description
#> [1] "Combinations of 5 choose 3"
#> 
#> $currentIndex
#> [1] 11
#> 
#> $totalResults
#> [1] 10
#> 
#> $totalRemaining
#> [1] -1
```

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

### Example Usage of stdThreadMax

Source: https://jwood000.github.io/RcppAlgos/reference/stdThreadMax.html

Demonstrates the typical output of stdThreadMax(). The returned value is a hint and may vary across systems.

```R
stdThreadMax()
#> [1] 10
```

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

### Partition Vector into Groups with comboGroups

Source: https://jwood000.github.io/RcppAlgos/index.html

Efficiently partitions a vector into specified group sizes using RcppAlgos::comboGroups. This example finds all possible partitions of players into groups of size 2 and 3.

```R
players <- c("Ross", "Bobby", "Max", "Casper", "Jake")
comboGroups(players, grpSizes = c(2, 3))
```

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

### Permutations with Repetition (Fibonacci Example)

Source: https://jwood000.github.io/RcppAlgos/articles/GeneralCombinatorics.html

Generates permutations with repetition using a sequence of Fibonacci numbers. Shows that the class of the output matches the input.

```R
fibonacci <- c(1L, 2L, 3L, 5L, 8L, 13L, 21L, 34L)
permsFib <- permuteGeneral(fibonacci, 5, TRUE)

ht(permsFib)
```

```R
#> head -->
#>      [,1] [,2] [,3] [,4] [,5]
#> [1,]    1    1    1    1    1
#> [2,]    1    1    1    1    2
#> [3,]    1    1    1    1    3
#> [4,]    1    1    1    1    5
#> [5,]    1    1    1    1    8
#> --------
#> tail -->
#>          [,1] [,2] [,3] [,4] [,5]
#> [32764,]   34   34   34   34    5
#> [32765,]   34   34   34   34    8
#> [32766,]   34   34   34   34   13
#> [32767,]   34   34   34   34   21
#> [32768,]   34   34   34   34   34

## N.B. class is preserved
class(fibonacci)
#> [1] "integer"

class(permsFib[1, ])
#> [1] "integer"
```

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

### Iterating Over Compositions

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Demonstrates how to iterate over compositions of a number using compositionsIter. Shows how to get the next iteration, current iteration, and summary statistics. Random access is supported, but previous iteration is not.

```R
p = compositionsIter(6, 3, TRUE)
p@nextIter()
#> [1] 1 1 4

p@nextIter()
#> [1] 1 2 3

iter = p@currIter()
i = 1

while (!is.null(iter)) {
    cat(i, " ", iter, "\n")
    iter = p@nextIter()
    i = i + 1
}
#> 1   1 2 3 
#> 2   1 3 2 
#> 3   1 4 1 
#> 4   2 1 3 
#> 5   2 2 2 
#> 6   2 3 1 
#> 7   3 1 2 
#> 8   3 2 1 
#> 9   4 1 1 
#> No more results.
```

```R
compositionsGeneral(6, 3, TRUE, lower = 2)
#>       [,1] [,2] [,3]
#>  [1,]    1    2    3
#>  [2,]    1    3    2
#>  [3,]    1    4    1
#>  [4,]    2    1    3
#>  [5,]    2    2    2
#>  [6,]    2    3    1
#>  [7,]    3    1    2
#>  [8,]    3    2    1
#>  [9,]    4    1    1
```

```R
p@summary()
#> $description
#> [1] "Compositions with repetition of 6 into 3 parts"
#>
#> $currentIndex
#> [1] 11
#>
#> $totalResults
#> [1] 10
#>
#> $totalRemaining
#> [1] -1
```

```R
p[[7]]
#> [1] 2 3 1
```

```R
p@prevIter()
#> Error: no slot of name "prevIter" for this object of class "Partitions"
```

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

### Iterator Summary and Back Access

Source: https://jwood000.github.io/RcppAlgos/reference/comboGroupsIterator.html

Shows how to get a summary of the iterator's state using summary() and access the last element of the current partition using back().

```R
a@summary()
#> $description
#> [1] "Partition of v of length 12 into 3 uniform groups"
#> 
#> $currentIndex
#> [1] 5776
#> 
#> $totalResults
#> [1] 5775
#> 
#> $totalRemaining
#> [1] -1
#> 
a@back()
#> Grp1 Grp1 Grp1 Grp1 Grp2 Grp2 Grp2 Grp2 Grp3 Grp3 Grp3 Grp3 
#>    1   10   11   12    2    7    8    9    3    4    5    6 
```

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

### Basic Usage of comboGeneral with Constraint Function

Source: https://jwood000.github.io/RcppAlgos/articles/CombPermConstraints.html

Demonstrates using `comboGeneral` with the `constraintFun` parameter set to 'sum'. An additional column is appended to the output, showing the sum of each combination. This example also shows parallel processing and compares performance against base R's `combn`.

```R
library(RcppAlgos)
options(width = 90)

packageVersion("RcppAlgos")
#> [1] '2.10.0'

cat(paste(capture.output(sessionInfo())[1:3], collapse = "\n"))
#> R version 4.5.2 (2025-10-31)
#> Platform: aarch64-apple-darwin20
#> Running under: macOS Sequoia 15.7.4

## base R using combn and FUN
combnSum = combn(20, 10, sum)
algosSum = comboGeneral(20, 10, constraintFun = "sum")

## Notice the additional column (i.e. the 11th column)
head(algosSum)
#>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11]
#> [1,]    1    2    3    4    5    6    7    8    9    10    55
#> [2,]    1    2    3    4    5    6    7    8    9    11    56
#> [3,]    1    2    3    4    5    6    7    8    9    12    57
#> [4,]    1    2    3    4    5    6    7    8    9    13    58
#> [5,]    1    2    3    4    5    6    7    8    9    14    59
#> [6,]    1    2    3    4    5    6    7    8    9    15    60

identical(as.integer(combnSum), algosSum[,11])
#> [1] TRUE

## Using parallel
paralSum = comboGeneral(20, 10, constraintFun = "sum", Parallel = TRUE)
identical(paralSum, algosSum)
#> [1] TRUE

library(microbenchmark)
microbenchmark(serial = comboGeneral(20, 10, constraintFun = "sum"),
             parallel = comboGeneral(20, 10, constraintFun = "sum", Parallel = TRUE),
             combnSum = combn(20, 10, sum), unit = "relative")
#> Warning in microbenchmark(serial = comboGeneral(20, 10, constraintFun = "sum"), : less
#> accurate nanosecond times to avoid potential integer overflows
#> Unit: relative
#>      expr        min         lq       mean     median         uq       max neval
#>    serial   3.622962   3.609644   3.249072   3.497137   3.418335  2.047686   100
#>  parallel   1.000000   1.000000   1.000000   1.000000   1.000000  1.000000   100
#>  combnSum 162.354728 154.733496 135.879799 147.380454 139.765227 81.747219   100
```

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

### Partition 22 using table method with multiplicities

Source: https://jwood000.github.io/RcppAlgos/articles/IntegerPartitions.html

Achieves the same result as the previous example by utilizing the `table` method for specifying multiplicities. This offers an alternative way to define part constraints.

```R
partitionsGeneral(table(c(rep(0L, 4), 1:8)), 6, target = 22)
```

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

### Reset Iterator and Get Total Results

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Resets the iterator to the beginning and retrieves the total number of possible combinations. This is a common starting point for iterating.

```R
a$startOver()

## How many total combinations do we have?
a$summary()$totalResults
#> [1] 10
```

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

### Initialize partitionsIter with table method

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Initializes a partitions iterator using a table as input for the source vector.

```R
partitionsIter(
    v, m = NULL, target = NULL, nThreads = NULL, tolerance = NULL, ...
)
```

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

### Install RcppAlgos Package

Source: https://jwood000.github.io/RcppAlgos/index.html

Install the RcppAlgos package from CRAN or the development version from GitHub.

```r
install.packages("RcppAlgos")

## install the development version
devtools::install_github("jwood000/RcppAlgos")
```

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

### Get Max Concurrent Threads

Source: https://jwood000.github.io/RcppAlgos/reference/stdThreadMax.html

Call stdThreadMax() to get the number of concurrent threads supported by the system. If the value cannot be determined, it defaults to 1L.

```R
stdThreadMax()
```

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

### Generate Combinations Starting from a Specific Index

Source: https://jwood000.github.io/RcppAlgos/reference/comboGroups.html

Generate combinations using comboGroups, but start the output from a specific index. This is useful for paginating or retrieving a subset of combinations.

```R
total = comboGroupsCount(11, grpSizes = c(3, 3, 5))
```

```R
comboGroups(11, grpSizes = c(3, 3, 5), lower = total - 20)
```

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

### Generate Partitions with a Step of 24

Source: https://jwood000.github.io/RcppAlgos/articles/OtherCombinatorics.html

Illustrates generating partitions by stepping through a sequence with an interval of 24, demonstrating potential duplication issues. This approach is less efficient than dedicated algorithms.

```R
do.call(rbind, lapply(seq(1, 169, 24), function(x) {
    funBruteGrp(myLow = x, myUp = x)
}))
#>     Grp1          Grp2           Grp3            
#> 1   "( 1 2 3 4 )" "( 5 6 7 8 )"  "( 9 10 11 12 )"
#> 25  "( 1 2 3 4 )" "( 5 6 7 9 )"  "( 8 10 11 12 )"
#> 49  "( 1 2 3 4 )" "( 5 6 7 10 )" "( 8 9 11 12 )" 
#> 73  "( 1 2 3 4 )" "( 5 6 7 11 )" "( 8 9 10 12 )"
#> 97  "( 1 2 3 4 )" "( 5 6 7 12 )" "( 8 9 10 11 )"
#> 121 "( 1 2 3 4 )" "( 5 6 8 7 )"  "( 9 10 11 12 )"  ### <-- This is the same as the 1st
#> 145 "( 1 2 3 4 )" "( 5 6 8 9 )"  "( 7 10 11 12 )"  ### partition. The only difference is
#> 169 "( 1 2 3 4 )" "( 5 6 8 10 )" "( 7 9 11 12 )"   ### that the 2nd Grp has been permuted
```

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

### RcppAlgos partitionsSample and compositionsSample Usage

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsSample.html

Demonstrates the basic usage of the `partitionsSample` and `compositionsSample` functions, including their default S3 methods.

```R
partitionsSample(v, m = NULL, ...)
compositionsSample(v, m = NULL, ...)

# Default S3 method
partitionsSample(
    v, m = NULL, repetition = FALSE, freqs = NULL, target = NULL,
    n = NULL, sampleVec = NULL, seed = NULL,
    nThreads = NULL, namedSample = FALSE, ...
)
# Default S3 method
compositionsSample(
    v, m = NULL, repetition = FALSE, freqs = NULL, target = NULL,
    weak = FALSE, n = NULL, sampleVec = NULL, seed = NULL,
    nThreads = NULL, namedSample = FALSE, ...
)

# S3 method for class 'table'
partitionsSample(
    v, m = NULL, target = NULL, n = NULL,
    sampleVec = NULL, seed = NULL, nThreads = NULL, namedSample = FALSE, ...
)
# S3 method for class 'table'
compositionsSample(
    v, m = NULL, target = NULL, weak = FALSE, n = NULL,
    sampleVec = NULL, seed = NULL, nThreads = NULL, namedSample = FALSE, ...
)
```

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

### Iterate Through Combinations

Source: https://jwood000.github.io/RcppAlgos/reference/combinatoricsIterator.html

Demonstrates how to retrieve individual combinations and multiple combinations sequentially from an iterator object. Use `@nextIter()` to get the next single combination and `@nextNIter(n)` to get the next `n` combinations.

```R
b@nextIter()
#> [1] 1056.087 1038.314 1036.531 1035.189 1029.416 1026.804 1025.575
```

```R
b@nextNIter(3)
#>          [,1]     [,2]     [,3]     [,4]     [,5]     [,6]     [,7]
#> [1,] 1056.087 1038.314 1036.531 1035.189 1029.416 1026.804 1024.763
#> [2,] 1056.087 1038.314 1036.531 1035.189 1029.416 1026.804 1021.563
#> [3,] 1056.087 1038.314 1036.531 1035.189 1029.416 1026.804 1019.610
```

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

### Get current iteration of iterator

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Returns the current iteration number of the iterator.

```R
currIter
```

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

### Initialize partitionsIter

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Initializes an iterator for partitions. Supports various arguments for customization, including repetition, frequencies, and target number.

```R
partitionsIter(v, m = NULL, repetition = FALSE,
               freqs = NULL, target = NULL,
               nThreads = NULL, tolerance = NULL, ...)
```

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

### General Partitions with Custom Frequencies and Targets

Source: https://jwood000.github.io/RcppAlgos/articles/SubsetSum.html

Illustrates using partitionsGeneral with a randomly sampled vector, custom frequencies, and a specific target sum. It also shows how to limit the number of results returned for performance.

```r
set.seed(42)
mySamp <- sample(-100:100, 50)

sort(mySamp)
#>  [1] -98 -97 -96 -95 -81 -77 -74 -65 -60 -59 -58 -54 -52 -43 -36 -33 -30 -27 -12  -9  -2
#> [22]  -1   3   8   9  10  13  21  27  30  33  35  42  45  49  52  53  57  61  63  64  70
#> [43]  73  76  83  84  88  91  96 100

system.time(exotic <- partitionsGeneral(mySamp, 8, freqs = rep(1:5, 10),
                                        target = 496))
#>    user  system elapsed 
#>   0.098   0.001   0.099

dim(exotic)
#> [1] 102241      8

## Over 1 billion total combinations
prettyNum(comboCount(mySamp, 8, freqs = rep(1:5, 10)), big.mark = ",")
#> [1] "1,343,133,680"

## Only getting a few (a thousand in this case) is much faster
system.time(partitionsGeneral(mySamp, 8, freqs = rep(1:5, 10),
                              target = 496, upper = 1e3))
#>    user  system elapsed 
#>   0.002   0.000   0.001

```

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

### Basic usage of partitionsSample with seed

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatorialSampling.html

Demonstrates the basic usage of partitionsSample to draw random samples of partitions. The 'seed' parameter ensures reproducible results.

```R
partitionsSample(100, 8, TRUE, n = 3, seed = 42)
#>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> [1,]    1    1    3    3    4   20   23   45
#> [2,]    1    1    2    7   14   14   29   32
#> [3,]    2   10   11   11   16   16   16   18
```

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

### General Combinations with Constraints

Source: https://jwood000.github.io/RcppAlgos/reference/RcppAlgos-package.html

Example of generating combinations with specific constraints, utilizing parallel processing for performance.

```R
comboGeneral(150, 5, constraintFun = "sum", Parallel = TRUE)
```

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

### Compare Serial vs. Multithreaded Partitions Generation

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Demonstrates how to use partitionsIterator with and without multithreading. Multithreading is only effective for large numbers of elements. Use microbenchmark to compare performance.

```R
serial   <- partitionsIter(1000, 10)
multi    <- partitionsIter(1000, 10, nThreads = 4)
fetch1e6 <- multi@nextNIter(1e6)  ## much faster than serial@nextNIter(1e6)
fetch1e3 <- multi@nextNIter(1e3)  ## only one thread used... same as serial@nextNIter(1e3)library(microbenchmark)
microbenchmark(multi@nextNIter(1e6), serial@nextNIter(1e6))
microbenchmark(multi@nextNIter(1e3), serial@nextNIter(1e3))
```

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

### partitionsIter() and compositionsIter()

Source: https://jwood000.github.io/RcppAlgos/reference/index.html

These functions provide iterators for generating partitions and compositions, enabling efficient processing of large numbers.

```APIDOC
## partitionsIter()

### Description
Provides an iterator for generating partitions.

### Method
`partitionsIter(n)`

### Parameters
- **n** (integer) - The integer to partition.

### Returns
An iterator object for partitions.

## compositionsIter()

### Description
Provides an iterator for generating compositions.

### Method
`compositionsIter(n)`

### Parameters
- **n** (integer) - The integer to compose.

### Returns
An iterator object for compositions.
```

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

### Get Previous Combinations with prevNIter

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Retrieves a specified number of previous combinations. This is useful for iterating backward through the results.

```R
a$prevNIter(4)
#>      [,1] [,2] [,3]
#> [1,]    3    4    5
#> [2,]    2    4    5
#> [3,]    2    3    5
#> [4,]    2    3    4
```

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

### Iterate through partitions with repetition

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Initialize an iterator for partitions with repetition and demonstrate fetching single partitions, multiple partitions, the front partition, remaining partitions, and summary information.

```R
a = partitionsIter(0:10, repetition = TRUE)
a@nextIter()
a@nextNIter(3)
a@front()
a@nextRemaining()
a@summary()
a@back()
a[[5]]
a[[c(1, 17, 3)]]
a@summary()
```

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

### Use Pre-computed Factorizations

Source: https://jwood000.github.io/RcppAlgos/reference/divisorsSieve.html

Demonstrates how to use the pre-computed factorizations generated by divisorsSieve for further analysis. Accessing the factorizations by index is efficient.

```R
## Use generated complete factorization for further
## analysis by accessing the index of allFacs
for (s in mySamp) {
    myFac <- allFacs[[s]]
    ## Continue algorithm
}
```

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

### Get Remaining Combinations with nextRemaining

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Retrieves the remaining combinations from the current iterator position. Assumes the iterator has been initialized.

```R
a$nextRemaining()
#>      [,1] [,2] [,3]
#> [1,]    1    3    5
#> [2,]    1    4    5
#> [3,]    2    3    4
#> [4,]    2    3    5
#> [5,]    2    4    5
#> [6,]    3    4    5
```

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

### Get summary information of iterator

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsIterator.html

Returns a list containing summary information about the iterator's state and configuration.

```R
summary
```

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

### Permutation Sampling with Frequencies

Source: https://jwood000.github.io/RcppAlgos/reference/RcppAlgos-package.html

Example of sampling permutations from a set while considering element frequencies. A seed is used for reproducibility.

```R
permuteSample(rnorm(100), 10, freqs = rep(1:4, 25), n = 15, seed = 123)
```

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

### Benchmark: Compositions (General, Repetition)

Source: https://jwood000.github.io/RcppAlgos/articles/HighPerformanceBenchmarks.html

Compares RcppAlgos (serial) with 'arrangements' and 'partitions' for generating all compositions of 15 with repetition. Excludes 'partitions' for larger cases due to efficiency.

```R
stopifnot(identical(dim(t1), dim(t2)), identical(dim(t1), dim(t(t3)))),
          all(rowSums(t1) == 15), all(rowSums(t2) == 15),
          all(colSums(t3) == 15))
dim(t1)
#> [1] 16384    15
rm(t1, t2, t3)
invisible(gc())
microbenchmark(cbRcppAlgosSer = compositionsGeneral(0:15, repetition = TRUE),
               cbArrangements = arrangements::compositions(15),
               cbPartitions   = partitions::compositions(15),
               times = 20, unit = "relative")
#> Unit: relative
#>            expr     min      lq    mean  median      uq     max neval
#>  cbRcppAlgosSer   1.107   1.101   1.098   1.096   1.094   1.053    20
#>  cbArrangements   1.000   1.000   1.000   1.000   1.000   1.000    20
#>    cbPartitions 110.419 117.834 145.577 145.641 165.113 191.249    20
```

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

### partitionsSample with namedSample and sampleVec

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatorialSampling.html

Shows how to use partitionsSample with 'namedSample = TRUE' to obtain lexicographical indices and with 'sampleVec' to retrieve specific partitions.

```R
partitionsSample(100, 8, TRUE, n = 3, seed = 42, namedSample = TRUE)
#>        [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> 61413     1    1    3    3    4   20   23   45
#> 54425     1    1    2    7   14   14   29   32
#> 623844    2   10   11   11   16   16   16   18

partitionsSample(100, 8, TRUE, sampleVec = c(61413, 54425, 623844))
#>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> [1,]    1    1    3    3    4   20   23   45
#> [2,]    1    1    2    7   14   14   29   32
#> [3,]    2   10   11   11   16   16   16   18
```

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

### Generate Partitions in Chunks

Source: https://jwood000.github.io/RcppAlgos/reference/partitionsGeneral.html

Demonstrates using the `lower` and `upper` arguments to generate partitions within a specific range, useful for parallel processing.

```R
partitionsGeneral(15, 3, lower = 6)
partitionsGeneral(15, 3, upper = 5)
```

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

### Get Current Combination

Source: https://jwood000.github.io/RcppAlgos/reference/combinatoricsIterator.html

Fetches the combination currently pointed to by the iterator. Use `@currIter()` to view the most recently generated or selected combination.

```R
b@currIter()
#> [1] 1056.087 1038.314 1036.531 1035.189 1029.416 1026.804 1019.610
```

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

### Generate Compositions with Distinct Parts Instantly using Threads

Source: https://jwood000.github.io/RcppAlgos/articles/IntegerCompositions.html

Shows how using multiple threads (nThreads = 4) can generate compositions with distinct parts almost instantly, significantly reducing the elapsed time.

```R
system.time(compositionsGeneral(55, 8, nThreads = 4))
#>    user  system elapsed 
#>   0.645   0.017   0.189
```

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

### Return Named List of Factorizations

Source: https://jwood000.github.io/RcppAlgos/reference/divisorsRcpp.html

Shows how to get a named list of factorizations when processing a vector of numbers by setting `namedList = TRUE`.

```R
## Return named list
myFacsWithNames <- divisorsRcpp(myVec, namedList = TRUE)
```

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

### Generate All Integer Partitions of N

Source: https://jwood000.github.io/RcppAlgos/articles/IntegerPartitions.html

Use `partitionsGeneral` with `repetition = TRUE` and `m = NULL` to find all possible ways to sum to N using positive integers, allowing parts to repeat. The `v` argument should be a sequence from 0 to N.

```R
library(RcppAlgos)
options(width = 90)

packageVersion("RcppAlgos")
#> [1] '2.10.0'

cat(paste(capture.output(sessionInfo())[1:3], collapse = "\n"))
#> R version 4.5.2 (2025-10-31)
#> Platform: aarch64-apple-darwin20
#> Running under: macOS Sequoia 15.7.4

partitionsGeneral(0:5, repetition = TRUE)
#>      [,1] [,2] [,3] [,4] [,5]
#> [1,]    0    0    0    0    5
#> [2,]    0    0    0    1    4
#> [3,]    0    0    0    2    3
#> [4,]    0    0    1    1    3
#> [5,]    0    0    1    2    2
#> [6,]    0    1    1    1    2
#> [7,]    1    1    1    1    1

## Note that we could also use comboGeneral:
## comboGeneral(0:5, repetition = TRUE,
##              constraintFun = "sum",
##              comparisonFun = "==", limitConstraints = 5)
##
## The same goes for any of the examples below
```

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

### Benchmark RcppAlgos Version 2.10.0 Iterators

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Measures the performance of the test_nextIter function for version 2.10.0 using microbenchmark. Ensure RcppAlgos is installed.

```r
curr_version <- as.integer(gsub("\.", "", packageVersion("RcppAlgos")))
curr_version
#> [1] 2100
microbenchmark(curr_v = test_nextIter(15, 8, v = curr_version))
#> Unit: milliseconds
#>    expr      min       lq     mean  median       uq      max neval
#>  curr_v 1.883376 1.960046 2.010785 1.99299 2.011481 2.722359   100
```

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

### Get Complete Factorization of a Single Number

Source: https://jwood000.github.io/RcppAlgos/reference/divisorsRcpp.html

Demonstrates how to obtain the complete factorization for a single integer using divisorsRcpp. The output is an unnamed vector.

```R
## Get the complete factorization of a single number
divisorsRcpp(10^8)
#>  [1]         1         2         4         5         8        10        16
#>  [8]        20        25        32        40        50        64        80
#> [15]       100       125       128       160       200       250       256
#> [22]       320       400       500       625       640       800      1000
#> [29]      1250      1280      1600      2000      2500      3125      3200
#> [36]      4000      5000      6250      6400      8000     10000     12500
#> [43]     15625     16000     20000     25000     31250     32000     40000
#> [50]     50000     62500     78125     80000    100000    125000    156250
#> [57]    160000    200000    250000    312500    390625    400000    500000
#> [64]    625000    781250    800000   1000000   1250000   1562500   2000000
#> [71]   2500000   3125000   4000000   5000000   6250000  10000000  12500000
#> [78]  20000000  25000000  50000000 100000000
```

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

### Sample Partitions with Restrictions

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatorialSampling.html

Demonstrates sampling partitions of a number with frequency constraints. The `target` parameter can be used to restrict the sum of elements in the partition.

```R
partitionsSample(0:50, 6, freqs = c(50, rep(1, 50)),
                 n = 3, seed = 222, target = 100)
```

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

### Accessing First and Remaining Elements

Source: https://jwood000.github.io/RcppAlgos/reference/comboGroupsIterator.html

Demonstrates retrieving the first element of the current partition using front() and all remaining elements using nextRemaining().

```R
a@front()
#> Grp1 Grp1 Grp1 Grp1 Grp2 Grp2 Grp2 Grp2 Grp3 Grp3 Grp3 Grp3 
#>    1    2    3    4    5    6    7    8    9   10   11   12 
all_remaining = a@nextRemaining()
dim(all_remaining)
#> [1] 5774   12
```

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

### Constrained Combinations with comboGeneral

Source: https://jwood000.github.io/RcppAlgos/index.html

Generate combinations that satisfy specific constraints, such as a product range. This example finds combinations where the product is between 3600 and 4000.

```r
## Get combinations such that the product is between
## 3600 and 4000 (including 3600 but not 4000)
comboGeneral(5, 7, TRUE, constraintFun = "prod",
             comparisonFun = c(">=","<"),
             limitConstraints = c(3600, 4000),
             keepResults = TRUE)
#>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> [1,]    1    2    3    5    5    5    5 3750
#> [2,]    1    3    3    4    4    5    5 3600
#> [3,]    1    3    4    4    4    4    5 3840
#> [4,]    2    2    3    3    4    5    5 3600
#> [5,]    2    2    3    4    4    4    5 3840
#> [6,]    3    3    3    3    3    3    5 3645
#> [7,]    3    3    3    3    3    4    4 3888
```

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

### Verify RcppAlgos Version 2.10.0 Iterator Results

Source: https://jwood000.github.io/RcppAlgos/articles/CombinatoricsIterators.html

Compares the output of test_nextIter with comboGeneral for version 2.10.0 to ensure correctness. Ensure RcppAlgos is installed.

```r
identical(test_nextIter(15, 8, get_val = TRUE, v = curr_version),
          comboGeneral(15, 8))
#> [1] TRUE
```

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

### Using Multithreading for Factorization

Source: https://jwood000.github.io/RcppAlgos/reference/divisorsRcpp.html

Demonstrates how to utilize multiple threads for faster computation of factorizations by specifying the `nThreads` argument. Timing is included.

```R
## Using nThreads
system.time(divisorsRcpp(myVec, nThreads = 2))
#>    user  system elapsed 
#>   0.001   0.000   0.001 

```
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