H3 Geospatial Indexing System

https://h3geo.org/docs
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H3 is an open-source geospatial indexing system that partitions the world into hexagonal cells,...
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### Install H3 with Homebrew

Source: https://h3geo.org/docs/installation

Install the C library and filter applications using Homebrew.

```bash
brew install h3
```

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

### Install Build Dependencies

Source: https://h3geo.org/docs/installation

Install required build tools for macOS, Alpine, Debian/Ubuntu, and FreeBSD.

```bash
# Installing the bare build requirements

brew install cmake

# Installing useful tools for development

brew install clang-format lcov doxygen
```

```bash
# Installing the bare build requirements

apk add cmake make gcc libtool musl-dev
```

```bash
# Installing the bare build requirements

sudo apt install cmake make gcc libtool

# Installing useful tools for development

sudo apt install clang-format cmake-curses-gui lcov doxygen
```

```bash
# Installing the build requirements

sudo pkg install bash cmake gmake doxygen lcov
```

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

### Install H3 with Python

Source: https://h3geo.org/docs/installation

Use pip or conda to install the H3 Python bindings.

```bash
pip install h3
```

```bash
conda config --add channels conda-forge

conda install h3-py
```

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

### Install and Load H3 in DuckDB

Source: https://h3geo.org/docs/installation

Install the H3 extension from the community repository and load it into your DuckDB session.

```sql
INSTALL h3 FROM community;
```

```sql
LOAD h3;
```

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

### JavaScript Live Example

Source: https://h3geo.org/docs/api/regions

Demonstrates usage with a specific polygon and resolution.

```JavaScript
function example() {
    const polygon = [
        [37.813318999983238, -122.4089866999972145],
        [37.7198061999978478, -122.3544736999993603],
        [37.8151571999998453, -122.4798767000009008]
    ];
    const res = 7;
    return h3.polygonToCellsExperimental(polygon, res, h3.POLYGON_TO_CELLS_FLAGS.containmentOverlapping);
}
```

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

### localIjToCell Go implementation

Source: https://h3geo.org/docs/api/traversal

Go usage example for localIjToCell.

```Go
h3.LocalIJToCell(origin, CoordIJ{i, j})
```

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

### Get gridDiskDistances in Go

Source: https://h3geo.org/docs/api/traversal

Example usage of gridDiskDistances in Go.

```Go
cell.GridDiskDistances(k)  
```

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

### localIjToCell DuckDB implementation

Source: https://h3geo.org/docs/api/traversal

DuckDB usage example for localIjToCell.

```SQL
h3_local_ij_to_cell(origin, i, j)
```

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

### JavaScript gridDisk Usage

Source: https://h3geo.org/docs/api/traversal

JavaScript usage and example for gridDisk.

```javascript
h3.gridDisk(origin, k)
```

```javascript
function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.gridDisk(h, k);
}
```

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

### Install H3 with JavaScript

Source: https://h3geo.org/docs/installation

Use npm or yarn to add the h3-js package to your project.

```bash
npm install h3-js
```

```bash
yarn add h3-js
```

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

### Get gridDiskDistances in Shell

Source: https://h3geo.org/docs/api/traversal

Command line interface help for gridDiskDistances.

```Shell
$ h3 gridDiskDistances --help  

h3: Returns an array of arrays of H3 cells, each array containing cells 'k' steps away from the origin cell, based on the outer array index  

H3 4.1.0  

  

	gridDiskDistances	Returns an array of arrays of H3 cells, each array containing cells 'k' steps away from the origin cell, based on the outer array index  

	-h, --help	Show this help message.  

	-c, --cell <index>	Required. H3 Cell  

	-k <distance>	Required. Maximum grid distance for the output set  

	-f, --format <FMT>	'json' for [["CELL", ...], ...], 'newline' for CELL\n with an extra newline between rings (Default: json)  
```

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

### Get gridDiskDistances in JavaScript

Source: https://h3geo.org/docs/api/traversal

Example usage of gridDiskDistances in JavaScript.

```JavaScript
h3.gridDiskDistances(origin, k)  
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.gridDiskDistances(h, k);
}
```

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

### JavaScript childPosToCell usage

Source: https://h3geo.org/docs/api/hierarchy

Example usage of the JavaScript API.

```JavaScript
h3.childPosToCell(childPos, parent, childRes);
```

```JavaScript
function example() {
  const parent = '85283473fffffff';
  const childPos = 42;
  return h3.childPosToCell(childPos, parent, 7);
}
```

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

### Get gridDiskDistances in DuckDB

Source: https://h3geo.org/docs/api/traversal

Example usage of gridDiskDistances in DuckDB.

```SQL
h3_grid_disk_distances(origin, k)  
```

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

### localIjToCell JavaScript implementation

Source: https://h3geo.org/docs/api/traversal

JavaScript usage example for localIjToCell.

```JavaScript
h3.localIjToCell(origin, coords)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  const coords = {i: 0, j: 0};
  return h3.localIjToCell(h, coords);
}
```

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

### localIjToCell Python implementation

Source: https://h3geo.org/docs/api/traversal

Python usage example for localIjToCell.

```Python
h3.local_ij_to_cell(origin, i, j)
```

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

### Shell CLI Usage Example

Source: https://h3geo.org/docs/api/regions

Demonstrates how to use the command-line tool to calculate the maximum cell count for a specific polygon at a given resolution.

```Shell
$ h3 maxPolygonToCellsSize -r 7 -p "[[37.813318999983238, -122.4089866999972145], [37.7198061999978478, -122.3544736999993603], [37.8151571999998453, -122.4798767000009008]]"

100
```

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

### Install H3 with Java

Source: https://h3geo.org/docs/installation

Add the H3 dependency to your Maven or Gradle build configuration.

```xml
<dependency>

    <groupId>com.uber</groupId>

    <artifactId>h3</artifactId>

    <version>4.3.0</version>

</dependency>
```

```gradle
compile("com.uber:h3:4.3.0")
```

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

### JavaScript cellToChildPos usage

Source: https://h3geo.org/docs/api/hierarchy

Example usage of the JavaScript binding.

```JavaScript
h3.cellToChildPos(child, parentRes)
```

```JavaScript
function example() {
  const cell = '85283473fffffff';
  return h3.cellToChildPos(cell, 3);
}
```

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

### cellToVertex JavaScript implementation

Source: https://h3geo.org/docs/api/vertex

Example usage of the cellToVertex function in JavaScript.

```JavaScript
h3.cellToVertex(origin, vertexNum)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  const vertexNum = 2;
  return h3.cellToVertex(h, vertexNum);
}
```

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

### JavaScript cellToChildren usage

Source: https://h3geo.org/docs/api/hierarchy

Example of retrieving children for a specific cell index.

```JavaScript
h3.cellToChildren(cell, childRes)  
```

```JavaScript
function example() {
  const cell = '85283473fffffff';
  return h3.cellToChildren(cell, 6);
}
```

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

### Set Boolean CMake Option

Source: https://h3geo.org/docs/core-library/compilation-options

Example of toggling a boolean CMake option between ON and OFF.

```cmake
cmake .. -DBUILD_TESTING=OFF
```

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

### Set CMake Build Type

Source: https://h3geo.org/docs/core-library/compilation-options

Example of setting a CMake variable using the -D flag on the command line.

```cmake
cmake .. -DCMAKE_BUILD_TYPE=Release
```

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

### Get gridDiskDistances in C

Source: https://h3geo.org/docs/api/traversal

Produces a set of cells along with their grid distance from the origin.

```C
H3Error gridDiskDistances(H3Index origin, int k, H3Index* out, int* distances);  
```

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

### Get Pentagons at Resolution

Source: https://h3geo.org/docs/api/misc

Retrieves all 12 pentagon H3 cells for a specified resolution.

```c
H3Error getPentagons(int res, H3Index *out);
```

```java
Collection<Long> h3.getPentagons(int res);

Collection<String> h3.getPentagonsAddresses(int res);
```

```javascript
h3.getPentagons(res)
```

```javascript
function example() {
  const res = 5;
  return h3.getPentagons(res);
}
```

```python
h3.get_pentagons(res)
```

```go
h3.Pentagons(res)
```

```duckdb
h3_get_pentagons(res)
```

```duckdb
h3_get_pentagons_string(res)
```

```shell
$ h3 getPentagons --help

h3: Returns all of the pentagons at the specified resolution

H3 4.1.0

  

	getPentagons	Returns all of the pentagons at the specified resolution

	-r, --resolution <res>	Required. Resolution, 0-15 inclusive.

	-h, --help	Show this help message.

	-f, --format <FMT>	'json' for ["CELL", ...], 'newline' for CELL\n... (Default: json)
```

```shell
$ h3 getPentagons -r 5

[ "85080003fffffff", "851c0003fffffff", "85300003fffffff", "854c0003fffffff", "85620003fffffff", "85740003fffffff", "857e0003fffffff", "85900003fffffff", "85a60003fffffff", "85c20003fffffff", "85d60003fffffff", "85ea0003fffffff" ]
```

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

### Shell CLI Help for maxPolygonToCellsSize

Source: https://h3geo.org/docs/api/regions

Displays the help menu for the command-line interface version of the function.

```Shell
$ h3 maxPolygonToCellsSize --help
```

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

### Run H3 Tests and Verify

Source: https://h3geo.org/docs/installation

Execute the test suite and verify the filter applications.

```bash
ctest
```

```bash
./bin/latLngToCell --lat 14 --lng -42 --resolution 2
```

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

### Go polygonToCellsExperimental usage

Source: https://h3geo.org/docs/api/regions

Standard implementation for Go environments.

```Go
h3.PolygonToCellsExperimental(polygon, res, containmentMode, maxNumCellsReturn)
```

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

### Clone and Checkout H3 Source

Source: https://h3geo.org/docs/installation

Retrieve the source code from the repository and checkout the latest release.

```bash
git clone https://github.com/uber/h3.git

cd h3

git checkout v$(<VERSION)
```

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

### gridPathCells CLI Usage

Source: https://h3geo.org/docs/api/traversal

Command line interface usage for the gridPathCells tool.

```Shell
$ h3 gridPathCells --help
```

```Shell
$ h3 gridPathCells -o 85283473fffffff -d 8528342bfffffff
```

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

### Go gridDisk Usage

Source: https://h3geo.org/docs/api/traversal

Go usage for gridDisk.

```go
cell.GridDisk(k)
```

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

### Shell CLI childPosToCell usage

Source: https://h3geo.org/docs/api/hierarchy

Command line interface usage for childPosToCell.

```Shell
$ h3 childPosToCell --help

h3: Returns the child cell at a given position and resolution within an ordered list of all children of the parent cell

H3 4.1.0

  

	childPosToCell	Returns the child cell at a given position and resolution within an ordered list of all children of the parent cell

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell

	-r, --resolution <res>	Required. Resolution, 1-15 inclusive, excluding 0 as it can never be a child

	-p, --position <pos>	Required. The child position within the set of children of the parent cell

	-f, --format <FMT>	'json' for "CELL"\n, 'newline' for CELL\n (Default: json)
```

```Shell
$ h3 childPosToCell -p 42 -c 85283473fffffff -r 7

"872834730ffffff"
```

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

### Implement Custom Memory Allocation Functions

Source: https://h3geo.org/docs/core-library/custom-alloc

Define the required memory management functions in your application using the prefix specified during the build.

```c
void* my_prefix_malloc(size_t size);  

void* my_prefix_calloc(size_t num, size_t size);  

void* my_prefix_realloc(void* ptr, size_t size);  

void my_prefix_free(void* ptr);  
```

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

### Get Directed Edge Destination

Source: https://h3geo.org/docs/api/uniedge

Retrieves the destination hexagon from a directed edge H3Index.

```C
H3Error getDirectedEdgeDestination(H3Index edge, H3Index *out);
```

```Java
long getDirectedEdgeDestination(long edge);

String getDirectedEdgeDestination(String edgeAddress);
```

```JavaScript
h3.getDirectedEdgeDestination(edge)
```

```JavaScript
function example() {
  const edge = '115283473fffffff';
  return h3.getDirectedEdgeDestination(edge);
}
```

```Python
h3.get_directed_edge_destination(edge)
```

```Go
edge.Destination()
```

```DuckDB
h3.get_directed_edge_destination(edge)
```

```Shell
$ h3 getDirectedEdgeDestination --help

h3: Returns the destination cell from the directed edge

H3 4.1.0

  

	getDirectedEdgeDestination	Returns the destination cell from the directed edge

	-c, --cell <index>	Required. H3 Cell

	-h, --help	Show this help message.

	-f, --format <FMT>	'json' for "CELL"\n, 'newline' for CELL\n (Default: json)
```

```Shell
$ h3 getDirectedEdgeDestination -c 115283473fffffff

"85283477fffffff"
```

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

### Get Directed Edge Origin

Source: https://h3geo.org/docs/api/uniedge

Retrieves the origin hexagon from a directed edge H3Index.

```C
H3Error getDirectedEdgeOrigin(H3Index edge, H3Index *out);
```

```Java
long getDirectedEdgeOrigin(long edge);

String getDirectedEdgeOrigin(String edgeAddress);
```

```JavaScript
h3.getDirectedEdgeOrigin(h3Index)
```

```JavaScript
function example() {
  const edge = '115283473fffffff';
  return h3.getDirectedEdgeOrigin(edge);
}
```

```Python
h3.get_directed_edge_origin(edge)
```

```Go
edge.Origin()
```

```DuckDB
h3_get_directed_edge_origin(edge)
```

```Shell
$ h3 getDirectedEdgeOrigin --help

h3: Returns the origin cell from the directed edge

H3 4.1.0

  

	getDirectedEdgeOrigin	Returns the origin cell from the directed edge

	-c, --cell <index>	Required. H3 Cell

	-h, --help	Show this help message.

	-f, --format <FMT>	'json' for "CELL"\n, 'newline' for CELL\n (Default: json)
```

```Shell
$ h3 getDirectedEdgeOrigin -c 115283473fffffff

"85283473fffffff"
```

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

### Calculate cellToChildrenSize in Shell

Source: https://h3geo.org/docs/api/hierarchy

Command line interface for calculating children size.

```Shell
$ h3 cellToChildrenSize --help
```

```Shell
$ h3 cellToChildrenSize -c 85283473fffffff -r 6
```

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

### Get Number of Cells

Source: https://h3geo.org/docs/api/misc

Retrieves the total count of unique H3 indexes at a specified resolution.

```C
H3Error getNumCells(int res, int64_t *out);
```

```Java
long getNumCells(int res);
```

```JavaScript
h3.getNumCells(res)
```

```JavaScript
function example() {
  const res = 5;
  return h3.getNumCells(res);
}
```

```Python
h3.get_num_cells(res)
```

```Go
h3.NumCells(res)
```

```DuckDB
h3_get_num_cells(res)
```

```Shell
$ h3 getNumCells --help
```

```Shell
$ h3 getNumCells -r 5
```

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

### cellToVertex Go implementation

Source: https://h3geo.org/docs/api/vertex

Go binding for the cellToVertex function.

```Go
h3.CellToVertex(origin, vertexNum)
```

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

### Calculate grid disk distances in Python

Source: https://h3geo.org/docs/api/traversal

Python interface for calculating grid disk distances.

```Python
h3_grid_disk_distances_safe(origin, k)
```

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

### Get Unidirectional Edge Length

Source: https://h3geo.org/docs/api/misc

Calculates the exact length of a specific unidirectional edge in kilometers.

```C
H3Error edgeLengthKm(H3Index edge, double *length);
```

```Java
double edgeLength(long h3, LengthUnit unit);

double edgeLength(String h3Address, LengthUnit unit);
```

```JavaScript
h3.edgeLength(h, h3.UNITS.km)
```

```JavaScript
function example() {
  const h = '115283473fffffff';
  return h3.edgeLength(h, h3.UNITS.km);
}
```

```Python
h3.edge_length(h, unit='km')
```

```Go
h3.EdgeLengthKm(edge)
```

```DuckDB
h3_edge_length(h, 'km')
```

```Shell
$ h3 edgeLengthKm --help
```

```Shell
$ h3 edgeLengthKm -c 115283473fffffff
```

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

### Calculate grid disk distances in C

Source: https://h3geo.org/docs/api/traversal

Calculates indexes within k distance of the origin index, storing results in provided arrays.

```C
H3Error gridDiskDistancesSafe(H3Index origin, int k, H3Index* out, int* distances);
```

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

### Retrieve parent cell in Java

Source: https://h3geo.org/docs/api/hierarchy

Provides methods to get the parent cell index or address.

```java
long cellToParent(long cell, int parentRes);  

String cellToParentAddress(String cellAddress, int parentRes);
```

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

### Get all directed edges from a cell

Source: https://h3geo.org/docs/api/uniedge

Retrieves all directed edges originating from the specified H3 cell.

```C
H3Error originToDirectedEdges(H3Index origin, H3Index* edges);
```

```Java
List<Long> originToDirectedEdges(long h3);

List<String> originToDirectedEdges(String h3);
```

```JavaScript
h3.originToDirectedEdges(h3Index)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  return h3.originToDirectedEdges(h);
}
```

```Python
h3.origin_to_directed_edges(h)
```

```Go
origin.DirectedEdges()
```

```DuckDB
h3_origin_to_directed_edges(h)
```

```Shell
$ h3 originToDirectedEdges --help
```

```Shell
$ h3 originToDirectedEdges -c 85283473fffffff
```

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

### Go uncompactCells usage

Source: https://h3geo.org/docs/api/hierarchy

The Go implementation uses PascalCase for the function name.

```Go
h3.UncompactCells(cells, res)
```

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

### Build H3 Library

Source: https://h3geo.org/docs/installation

Compile the H3 library from source using CMake.

```bash
mkdir build

cd build

cmake -DCMAKE_BUILD_TYPE=Release ..

cmake --build .
```

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

### Get Resolution 0 Cell Count

Source: https://h3geo.org/docs/api/misc

Returns the constant number of H3 indexes at resolution 0.

```c
int res0CellCount(void);
```

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

### Get gridDiskDistances in Java

Source: https://h3geo.org/docs/api/traversal

Retrieves grid distances using either long or String H3 indices.

```Java
List<List<Long>> gridDiskDistances(long origin, int k);  

List<List<String>> gridDiskDistances(String origin, int k);  
```

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

### Calculate grid disks in C

Source: https://h3geo.org/docs/api/traversal

Returns an array of cells sorted by original indices and grid ring, assuming no pentagonal distortion.

```C
H3Error gridDisksUnsafe(H3Index* h3Set, int length, int k, H3Index* out);
```

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

### CLI gridRing

Source: https://h3geo.org/docs/api/traversal

Command-line interface usage for the gridRing operation.

```APIDOC
## CLI: h3 gridRing

### Description
Returns an array of H3 cells, each cell 'k' steps away from the origin cell.

### Options
- **-c, --cell** (string) - Required - H3 Cell index.
- **-k** (integer) - Required - Maximum grid distance for the output set.
- **-f, --format** (string) - Optional - Output format ('json' or 'newline').

### Example
$ h3 gridRing -k 1 -c 85283473fffffff
```

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

### Get maxGridDiskSize in C

Source: https://h3geo.org/docs/api/traversal

Calculates the maximum number of cells resulting from a gridDisk operation for a given k.

```C
H3Error maxGridDiskSize(int k, int64_t *out);  
```

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

### Get H3 index resolution

Source: https://h3geo.org/docs/api/inspection

Retrieves the resolution of an H3 index, applicable to cells, edges, and vertexes.

```C
int getResolution(H3Index h);
```

```Java
int getResolution(long h3);

int getResolution(String h3Address);
```

```JavaScript
h3.getResolution(h)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  return h3.getResolution(h);
}
```

```Python
h3.get_resolution(h)
```

```Go
cell.Resolution()
```

```DuckDB
h3_get_resolution(h)
```

```Shell
$ h3 getResolution --help

h3: Extracts the resolution (0 - 15) from the H3 cell

H3 4.1.0

  

	getResolution	Extracts the resolution (0 - 15) from the H3 cell

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell
```

```Shell
$ h3 getResolution -c 85283473fffffff

5
```

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

### Go gridRing Usage

Source: https://h3geo.org/docs/api/traversal

Standard usage for the Go H3 library.

```Go
cell.GridRing(k)
```

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

### Get average hexagon area in square meters

Source: https://h3geo.org/docs/api/misc

Calculates the average area of a hexagon in m² for a given resolution.

```C
H3Error getHexagonAreaAvgM2(int res, double *out);
```

```Java
double getHexagonAreaAvg(int res, AreaUnit unit);
```

```JavaScript
h3.getHexagonAreaAvg(res, h3.UNITS.m2)
```

```JavaScript
function example() {
  const res = 5;
  return h3.getHexagonAreaAvg(res, h3.UNITS.m2);
}
```

```Python
h3.average_hexagon_area(res, unit='m^2')
```

```Go
h3.HexagonAreaAvgM2(res)
```

```DuckDB
h3_average_hexagon_area(res, 'm^2')
```

```Shell
$ h3 getHexagonAreaAvgM2 --help
```

```Shell
$ h3 getHexagonAreaAvgM2 -r 5
```

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

### compactCells Shell CLI

Source: https://h3geo.org/docs/api/hierarchy

Command line interface for compacting H3 cells.

```Shell
$ h3 compactCells --help

h3: Compacts the provided set of cells as best as possible. The set of input cells must all share the same resolution.

H3 4.1.0

  

	compactCells	Compacts the provided set of cells as best as possible. The set of input cells must all share the same resolution.

	-h, --help	Show this help message.

	-i, --file <FILENAME>	The file to load the cells from. Use -- to read from stdin.

	-c, --cells <CELLS>	The cells to compact. Up to 100 cells if provided as hexadecimals with zero padding.

	-f, --format <FMT>	'json' for ["CELL", ...], 'newline' for CELL\n... (Default: json)
```

```Shell
$ h3 compactCells -c 85283473fffffff,85283447fffffff,8528347bfffffff,85283463fffffff,85283477fffffff,8528340ffffffff,8528340bfffffff,85283457fffffff,85283443fffffff,8528344ffffffff,852836b7fffffff,8528346bfffffff,8528346ffffffff,85283467fffffff,8528342bfffffff,8528343bfffffff,85283407fffffff,85283403fffffff,8528341bfffffff

[ "85283447fffffff", "8528340ffffffff", "8528340bfffffff", "85283457fffffff", "85283443fffffff", "8528344ffffffff", "852836b7fffffff", "8528342bfffffff", "8528343bfffffff", "85283407fffffff", "85283403fffffff", "8528341bfffffff", "8428347ffffffff" ]
```

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

### Get average hexagon area in square kilometers

Source: https://h3geo.org/docs/api/misc

Calculates the average area of a hexagon in km² for a given resolution.

```C
H3Error getHexagonAreaAvgKm2(int res, double *out);
```

```Java
double getHexagonAreaAvg(int res, AreaUnit unit);
```

```JavaScript
h3.getHexagonAreaAvg(res, h3.UNITS.km2)
```

```JavaScript
function example() {
  const res = 5;
  return h3.getHexagonAreaAvg(res, h3.UNITS.km2);
}
```

```Python
h3.average_hexagon_area(res, unit='km^2')
```

```Go
h3.HexagonAreaAvgKm2(res)
```

```DuckDB
h3_average_hexagon_area(res, 'km^2')
```

```Shell
$ h3 getHexagonAreaAvgKm2 --help
```

```Shell
$ h3 getHexagonAreaAvgKm2 -r 1
```

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

### h3.PolygonToCellsExperimental (Go)

Source: https://h3geo.org/docs/api/regions

Go function for polygonToCellsExperimental.

```APIDOC
## h3.PolygonToCellsExperimental(polygon, res, containmentMode, maxNumCellsReturn)

### Description
Go implementation for H3 polygon to cells conversion.
```

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

### Shell CLI uncompactCells usage

Source: https://h3geo.org/docs/api/hierarchy

The CLI tool supports reading from arguments or files and outputting in JSON or newline-delimited formats.

```Shell
$ h3 uncompactCells --help
```

```Shell
$ h3 uncompactCells -r 5 -c 85283447fffffff,8528340ffffffff,8528340bfffffff,85283457fffffff,85283443fffffff,8528344ffffffff,852836b7fffffff,8528342bfffffff,8528343bfffffff,85283407fffffff,85283403fffffff,8528341bfffffff,8428347ffffffff
```

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

### Get Icosahedron Faces for H3 Index

Source: https://h3geo.org/docs/api/inspection

Finds all icosahedron faces (0-19) intersected by a given H3 cell.

```C
H3Error getIcosahedronFaces(H3Index h, int* out);
```

```Java
Collection<Integer> getIcosahedronFaces(long h3);

Collection<Integer> getIcosahedronFaces(String h3Address);
```

```JavaScript
h3.getIcosahedronFaces(h)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  return h3.getIcosahedronFaces(h);
}
```

```Python
h3.get_icosahedron_faces(h)
```

```Go
cell.IcosahedronFaces()
```

```DuckDB
h3_get_icosahedron_faces(h)
```

```Shell
$ h3 getIcosahedronFaces --help

h3: Returns the icosahedron face numbers (0 - 19) that the H3 index intersects

H3 4.1.0


	getIcosahedronFaces	Returns the icosahedron face numbers (0 - 19) that the H3 index intersects

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell

	-f, --format <FMT>	'json' for [faceNum, ...], 'newline' for faceNum\n... (Default: json)
```

```Shell
$ h3 getIcosahedronFaces -c 85283473fffffff

[7]
```

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

### h3.h3shape_to_cells_experimental (Python)

Source: https://h3geo.org/docs/api/regions

Python function for polygonToCellsExperimental.

```APIDOC
## h3.h3shape_to_cells_experimental(h3shape, res, contain='overlap')

### Description
Python function taking an H3Shape object to return cells.
```

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

### Get Average Hexagon Edge Length

Source: https://h3geo.org/docs/api/misc

Calculates the average edge length of hexagons at a specific resolution, excluding pentagons.

```C
H3Error getHexagonEdgeLengthAvgM(int res, double *out);
```

```Java
double getHexagonEdgeLengthAvg(int res, LengthUnit unit);
```

```JavaScript
h3.getHexagonEdgeLengthAvg(res, h3.UNITS.m)
```

```JavaScript
function example() {
  const res = 5;
  return h3.getHexagonEdgeLengthAvg(res, h3.UNITS.m);
}
```

```Python
h3.average_hexagon_edge_length(res, unit='m')
```

```Go
h3.HexagonEdgeLengthAvgM(res)
```

```DuckDB
h3_average_hexagon_edge_length(res, 'm')
```

```Shell
$ h3 getHexagonEdgeLengthAvgM --help
```

```Shell
$ h3 getHexagonEdgeLengthAvgM -r 5
```

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

### Get maximum face count in C

Source: https://h3geo.org/docs/api/inspection

This function is intended for internal memory management and is not exposed for public API usage.

```C
H3Error maxFaceCount(H3Index h3, int *out);
```

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

### Convert cells to multi-polygon via CLI

Source: https://h3geo.org/docs/api/regions

Command line interface usage for converting cells to multi-polygon formats.

```Shell
$ h3 cellsToMultiPolygon --help
```

```Shell
$ h3 cellsToMultiPolygon -c 872830828ffffff,87283082effffff
```

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

### Get origin and destination cells from a directed edge

Source: https://h3geo.org/docs/api/uniedge

Retrieves the origin and destination cells for a given directed edge index.

```C
H3Error directedEdgeToCells(H3Index edge, H3Index* originDestination);
```

```Java
List<Long> directedEdgeToCells(long edge);

List<String> directedEdgeToCells(String edgeAddress);
```

```JavaScript
h3.directedEdgeToCells(edge)
```

```JavaScript
function example() {
  const edge = '115283473fffffff';
  return h3.directedEdgeToCells(edge);
}
```

```Python
h3.directed_edge_to_cells(edge)
```

```Go
edge.Cells()
```

```DuckDB
h3_directed_edge_to_cells(edge)
```

```Shell
$ h3 directedEdgeToCells --help
```

```Shell
$ h3 directedEdgeToCells -c 115283473fffffff
```

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

### Go childPosToCell usage

Source: https://h3geo.org/docs/api/hierarchy

Go interface for the childPosToCell function.

```Go
parent.ChildPosToCell(childPos, res)
```

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

### Get H3 index base cell number

Source: https://h3geo.org/docs/api/inspection

Retrieves the base cell number of an H3 index, applicable to cells, edges, and vertexes.

```C
int getBaseCellNumber(H3Index h);
```

```Java
int getBaseCellNumber(long h3);

int getBaseCellNumber(String h3Address);
```

```JavaScript
h3.getBaseCellNumber(h)
```

```JavaScript
function example() {
  const h = '85283473fffffff';
  return h3.getBaseCellNumber(h);
}
```

```Python
h3.get_base_cell_number(h)
```

```Go
cell.BaseCellNumber()
```

```DuckDB
h3_get_base_cell_number(h)
```

```Shell
$ h3 getBaseCellNumber --help

h3: Extracts the base cell number (0 - 121) from the H3 cell

H3 4.1.0

  

	getBaseCellNumber	Extracts the base cell number (0 - 121) from the H3 cell

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell
```

```Shell
$ h3 getBaseCellNumber -c 85283473fffffff

20
```

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

### Get Resolution 0 Cells

Source: https://h3geo.org/docs/api/misc

Retrieves all 122 base cells at resolution 0. In C, the output array must be at least the size of res0CellCount().

```C
H3Error getRes0Cells(H3Index *out);
```

```Java
Collection<Long> getRes0Cells();
Collection<String> getRes0CellAddresses();
```

```JavaScript
h3.getRes0Cells()
```

```JavaScript
function example() {
  return h3.getRes0Cells();
}
```

```Python
h3.get_res0_cells()
```

```Go
h3.Res0Cells()
```

```DuckDB
h3_get_res0_cells()
```

```DuckDB
h3_get_res0_cells_string()
```

```Shell
$ h3 getRes0Cells --help
```

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

### Shell gridDisk CLI

Source: https://h3geo.org/docs/api/traversal

Shell command line interface usage for gridDisk.

```bash
$ h3 gridDisk --help

h3: Returns an array of a H3 cells within 'k' steps of the origin cell

H3 4.1.0

  

	gridDisk	Returns an array of a H3 cells within 'k' steps of the origin cell

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell

	-k <distance>	Required. Maximum grid distance for the output set

	-f, --format <FMT>	'json' for ["CELL", ...], 'newline' for CELL\n... (Default: json)
```

```bash
$ h3 gridDisk -k 5 -c 85283473fffffff

[ "85283473fffffff", "85283447fffffff", "8528347bfffffff", "85283463fffffff", "85283477fffffff", "8528340ffffffff", "8528340bfffffff", "85283457fffffff", "85283443fffffff", "8528344ffffffff", "852836b7fffffff", "8528346bfffffff", "8528346ffffffff", "85283467fffffff", "8528342bfffffff", "8528343bfffffff", "85283407fffffff", "85283403fffffff", "8528341bfffffff", "852834cffffffff", "85283453fffffff", "8528345bfffffff", "8528344bfffffff", "852836b3fffffff", "852836a3fffffff", "852836a7fffffff", "852830d3fffffff", "852830d7fffffff", "8528309bfffffff", "85283093fffffff", "8528342ffffffff", "85283423fffffff", "85283433fffffff", "852834abfffffff", "85283417fffffff", "85283413fffffff", "852834c7fffffff", "852834c3fffffff", "852834cbfffffff", "8529a927fffffff", "8529a92ffffffff", "85283697fffffff", "85283687fffffff", "852836bbfffffff", "852836abfffffff", "852836affffffff", "852830dbfffffff", "852830c3fffffff", "852830c7fffffff", "8528308bfffffff", "85283083fffffff", "85283097fffffff", "8528355bfffffff", "85283427fffffff", "85283437fffffff", "852834affffffff", "852834a3fffffff", "852834bbfffffff", "8528348ffffffff", "8528348bfffffff", "852834d7fffffff", "852834d3fffffff", "852834dbfffffff", "8529a937fffffff", "8529a923fffffff", "8529a92bfffffff", "85283693fffffff", "85283683fffffff", "8528368ffffffff", "85283617fffffff", "85283607fffffff", "85283633fffffff", "85283637fffffff", "852830cbfffffff", "852830cffffffff", "8528301bfffffff", "85283013fffffff", "8528308ffffffff", "85283087fffffff", "8528354bfffffff", "85283543fffffff", "85283553fffffff", "852835cbfffffff", "852835dbfffffff", "852834a7fffffff", "852834b7fffffff", "852834b3fffffff", "85283487fffffff", "85283483fffffff", "8528349bfffffff", "85291a6ffffffff" ]
```

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

### polygonToCellsExperimental (Java)

Source: https://h3geo.org/docs/api/regions

Java method signatures for polygonToCellsExperimental.

```APIDOC
## List<Long> polygonToCellsExperimental(List<LatLng> points, List<List<LatLng>> holes, PolygonToCellsFlags flags, int res);
## List<String> polygonToCellExperimentalAddresses(List<LatLng> points, List<List<LatLng>> holes, PolygonToCellsFlags flags, int res);

### Description
Java methods to retrieve H3 cells or addresses within a polygon.
```

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

### C childPosToCell implementation

Source: https://h3geo.org/docs/api/hierarchy

Returns an H3Error code; 0 indicates success.

```C
H3Error childPosToCell(int64_t childPos, H3Index parent, int childRes, H3Index *child);
```

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

### Calculate grid disk distances via CLI

Source: https://h3geo.org/docs/api/traversal

Use the gridDiskDistances command to retrieve H3 cells grouped by their distance from a specified center cell.

```bash
$ h3 gridDiskDistances -k 5 -c 85283473fffffff
```

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

### polygonToCellsExperimental (C)

Source: https://h3geo.org/docs/api/regions

C function signature for polygonToCellsExperimental.

```APIDOC
## H3Error polygonToCellsExperimental(const GeoPolygon *geoPolygon, int res, uint32_t flags, int64_t size, H3Index *out);

### Description
Takes a GeoPolygon struct and preallocated memory to fill with covering cells.

### Parameters
- **geoPolygon** (const GeoPolygon *) - Required - The polygon structure.
- **res** (int) - Required - Target cell resolution.
- **flags** (uint32_t) - Required - Containment mode (0: center, 1: full, 2: overlapping, 3: overlapping_bbox).
- **size** (int64_t) - Required - Size of the out array.
- **out** (H3Index *) - Required - Preallocated memory for output cells.
```

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

### localIjToCell Shell implementation

Source: https://h3geo.org/docs/api/traversal

Shell command-line interface usage for localIjToCell.

```Shell
$ h3 localIjToCell --help

h3: Returns the H3 index from a local IJ coordinate anchored to an origin cell

H3 4.1.0

  

	localIjToCell	Returns the H3 index from a local IJ coordinate anchored to an origin cell

	-h, --help	Show this help message.

	-o, --origin <cell>	Required. The origin H3 cell

	-i <i>	Required. The I dimension of the IJ coordinate

	-j <j>	Required. The J dimension of the IJ coordinate

	-f, --format <FMT>	'json' for "CELL"\n, 'newline' for CELL\n (Default: json)
```

```Shell
$ h3 localIjToCell -o 85283473fffffff -i 0 -j 0

"85280003fffffff"
```

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

### Shell CLI cellToChildren usage

Source: https://h3geo.org/docs/api/hierarchy

Command line interface for interacting with H3 cell children.

```Shell
$ h3 cellToChildren --help  

h3: Returns an array of H3 indexes that are the children (or lower) of the provided cell  

H3 4.1.0  

  

	cellToChildren	Returns an array of H3 indexes that are the children (or lower) of the provided cell  

	-h, --help	Show this help message.  

	-c, --cell <index>	Required. H3 Cell  

	-r, --resolution <res>	Required. Resolution, 1-15 inclusive, excluding 0 as it can never be a child  

	-f, --format <FMT>	'json' for ["CELL", ...], 'newline' for CELL\n... (Default: json)  
```

```Shell
$ h3 cellToChildren -c 85283473fffffff -r 6  

[ "862834707ffffff", "86283470fffffff", "862834717ffffff", "86283471fffffff", "862834727ffffff", "86283472fffffff", "862834737ffffff" ]  
```

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

### cellToVertex C implementation

Source: https://h3geo.org/docs/api/vertex

Returns 0 (E_SUCCESS) on success.

```C
H3Error cellToVertex(H3Index origin, int vertexNum, H3Index *out);
```

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

### Describe H3Error via Shell

Source: https://h3geo.org/docs/api/misc

Use the h3 CLI tool to retrieve error descriptions or view help documentation.

```shell
$ h3 describeH3Error --help
```

```shell
$ h3 describeH3Error -e 5
```

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

### Java gridDisk Function

Source: https://h3geo.org/docs/api/traversal

Java method signatures for gridDisk.

```java
List<Long> gridDisk(long origin, int k);

List<String> gridDisk(String origin, int k);
```

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

### Shell CLI cellToChildPos usage

Source: https://h3geo.org/docs/api/hierarchy

Command line interface usage for the H3 tool.

```Shell
$ h3 cellToChildPos --help

h3: Returns the position of the child cell within an ordered list of all children of the cell's parent at the specified child resolution

H3 4.1.0

  

	cellToChildPos	Returns the position of the child cell within an ordered list of all children of the cell's parent at the specified child resolution

	-h, --help	Show this help message.

	-c, --cell <index>	Required. H3 Cell

	-r, --resolution <res>	Required. Resolution, 1-15 inclusive, excluding 0 as it can never be a child
```

```Shell
$ h3 cellToChildPos -c 85283473fffffff -r 3

25
```

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

### JavaScript polygonToCellsExperimental usage

Source: https://h3geo.org/docs/api/regions

Standard implementation for JavaScript environments.

```JavaScript
h3.polygonToCellsExperimental(polygon, res, flags, isGeoJson)
```

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

### Python gridDisk Usage

Source: https://h3geo.org/docs/api/traversal

Python usage for gridDisk.

```python
h3.grid_disk(origin, k)
```

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

### Calculate grid path size in C

Source: https://h3geo.org/docs/api/traversal

Calculates the number of cells in a path for memory allocation purposes.

```C
H3Error gridPathCellsSize(H3Index start, H3Index end, int64_t* size);
```

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

### C gridDiskDistancesUnsafe implementation

Source: https://h3geo.org/docs/api/traversal

Produces indexes within k distance of the origin, with undefined behavior if pentagonal distortion is encountered.

```C
H3Error gridDiskDistancesUnsafe(H3Index origin, int k, H3Index* out, int* distances);
```

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

### localIjToCell C implementation

Source: https://h3geo.org/docs/api/traversal

C function signature for localIjToCell. The mode parameter is reserved and must be set to 0.

```C
H3Error localIjToCell(H3Index origin, const CoordIJ *ij, uint32_t mode, H3Index *out);
```

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

### Calculate cellToCenterChild in Shell

Source: https://h3geo.org/docs/api/hierarchy

Command line interface for finding the center child.

```Shell
$ h3 cellToCenterChild --help
```

```Shell
$ h3 cellToCenterChild -c 85283473fffffff -r 7
```

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

### Java childPosToCell implementation

Source: https://h3geo.org/docs/api/hierarchy

Provides both long-based and String-based address variants.

```Java
long childPosToCell(long childPos, long parent, int childRes);

String childPosToCell(long childPos, String parentAddress, int childRes);
```

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

### C API for maxPolygonToCellsSize

Source: https://h3geo.org/docs/api/regions

Provides the C function signature for calculating the maximum number of cells needed for a given polygon and resolution.

```C
H3Error maxPolygonToCellsSize(const GeoPolygon *geoPolygon, int res, uint32_t flags, int64_t *out);
```

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

### CLI usage for areNeighborCells

Source: https://h3geo.org/docs/api/uniedge

Command line interface usage for checking if two cells are neighbors.

```Shell
$ h3 areNeighborCells --help

h3: Determines if the provided H3 cells are neighbors (have a shared border)

H3 4.1.0

  

	areNeighborCells	Determines if the provided H3 cells are neighbors (have a shared border)

	-o, --origin <CELL>	Required. Origin H3 Cell

	-d, --destination <CELL>	Required. Destination H3 Cell

	-h, --help	Show this help message.

	-f, --format <FMT>	'json' for true or false, 'numeric' for 1 or 0 (Default: json)
```

```Shell
$ h3 areNeighborCells -o 85283473fffffff -d 85283477fffffff

true
```

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

### cellToVertex Shell CLI usage

Source: https://h3geo.org/docs/api/vertex

Command line interface usage for the cellToVertex function.

```Shell
$ h3 cellToVertex --help
```

```Shell
$ h3 cellToVertex -v 2 -c 85283473fffffff
```

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

### Go cellToChildPos usage

Source: https://h3geo.org/docs/api/hierarchy

Go binding for the cellToChildPos function.

```Go
child.ChildPos(parentRes)
```

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

### Java gridDiskUnsafe implementation

Source: https://h3geo.org/docs/api/traversal

Java variants for gridDiskUnsafe, throwing a PentagonEncounteredException when distortion occurs.

```Java
List<List<Long>> gridDiskUnsafe(Long h3, int k) throws PentagonEncounteredException;

List<List<String>> gridDiskUnsafe(String h3Address, int k) throws PentagonEncounteredException;
```

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

### C gridDiskUnsafe implementation

Source: https://h3geo.org/docs/api/traversal

Produces cells within grid distance k of the origin cell, returning an error code if pentagonal distortion is encountered.

```C
H3Error gridDiskUnsafe(H3Index origin, int k, H3Index* out);
```

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

### DuckDB gridDisk Usage

Source: https://h3geo.org/docs/api/traversal

DuckDB usage for gridDisk.

```sql
h3_grid_disk(origin, k)
```

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

### DuckDB polygonToCellsExperimental variants

Source: https://h3geo.org/docs/api/regions

Provides variants for WKT and WKB input formats, returning either cells or strings.

```SQL
h3_polygon_wkt_to_cells_experimental(wkt, res, 'overlap')
```

```SQL
h3_polygon_wkt_to_cells_experimental_string(wkt, res, 'overlap')
```

```SQL
h3_polygon_wkb_to_cells_experimental(wkb, res, 'overlap')
```

```SQL
h3_polygon_wkb_to_cells_experimental_string(wkb, res, 'overlap')
```
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