Hierarchical grid functions - H3

import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem';

These functions permit moving between resolutions in the H3 grid system. The functions produce parent (coarser) or children (finer) cells.

h3ToParent

H3Index h3ToParent(H3Index h, int parentRes);

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h3.h3_to_parent(h, parent_res)

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java

long h3ToParent(long h3, int parentRes);
String h3ToParent(String h3Address, int parentRes);

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h3.h3ToParent(h3Index, parentRes)

function example() {
  const h = '85283473fffffff';
  return h3v3.h3ToParent(h, 4);
}

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Returns the parent (coarser) index containing h.

h3ToChildren

void h3ToChildren(H3Index h, int childRes, H3Index *children);

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h3.h3_to_children(h, child_res)

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java

List<Long> h3ToChildren(long h3, int childRes);
List<String> h3ToChildren(String h3Address, int childRes);

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h3.h3ToChildren(h3Index, childRes)

function example() {
  const h = '85283473fffffff';
  return h3v3.h3ToChildren(h, 6);
}

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Populates children with the indexes contained by h at resolution childRes. children must be an array of at least size maxH3ToChildrenSize(h, childRes).

maxH3ToChildrenSize

int maxH3ToChildrenSize(H3Index h, int childRes);

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:::note

This function exists for memory management and is not exposed.

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:::note

This function exists for memory management and is not exposed.

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:::note

This function exists for memory management and is not exposed.

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Returns the parent (coarser) index containing h.

h3ToCenterChild

H3Index h3ToCenterChild(H3Index h, int childRes);

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h3.h3_to_center_child(h3, child_res)

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java

long h3ToCenterChild(long h3, int childRes);
String h3ToCenterChild(String h3, int childRes);

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h3.h3ToCenterChild(h, childRes)

function example() {
  const h = '85283473fffffff';
  return h3v3.h3ToCenterChild(h, 7);
}

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Returns the center child (finer) index contained by h at resolution childRes.

compact

int compact(const H3Index *h3Set, H3Index *compactedSet, const int numHexes);

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h3.compact(hexes)

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java

List<Long> compact(Collection<Long> h3);
List<String> compactAddress(Collection<String> h3);

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h3.compact(hexes)

function example() {
  const h = '85283473fffffff';
  const nearby = h3.kRing(h, 4);
  return h3v3.compact(nearby);
}

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Compacts the set h3Set of indexes as best as possible, into the array compactedSet. compactedSet must be at least the size of h3Set in case the set cannot be compacted.

Returns 0 on success.

uncompact

int uncompact(const H3Index *compactedSet, const int numHexes, H3Index *h3Set, const int maxHexes, const int res);

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h3.uncompact(hexes, res)

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java

List<Long> uncompact(Collection<Long> h3, int res);
List<String> uncompactAddress(Collection<String> h3, int res);

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h3.uncompact(hexes, res)

function example() {
  const h = '85283473fffffff';
  const nearby = h3.kRing(h, 4);
  const compacted = h3.compact(nearby);
  return h3v3.uncompact(compacted, 5);
}

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Uncompacts the set compactedSet of indexes to the resolution res. h3Set must be at least of size maxUncompactSize(compactedSet, numHexes, res).

Returns 0 on success.

maxUncompactSize

int maxUncompactSize(const H3Index *compactedSet, const int numHexes, const int res)

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:::note

This function exists for memory management and is not exposed.

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:::note

This function exists for memory management and is not exposed.

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:::note

This function exists for memory management and is not exposed.

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Returns the size of the array needed by uncompact.