1TOPOMERGE(1)                     User Commands                    TOPOMERGE(1)
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NAME

6       topomerge  -  merges the source TopoJSON geometry collection, assigning
7       to the target
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SYNOPSIS

10       topomerge [options] <target=source> [file]
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DESCRIPTION

13       Merges polygons (or meshes lines) from the  specified  source  TopoJSON
14       geometry collection object, assigning to the target object.
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OPTIONS

17       -h, --help
18              Output usage information.
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20       -V, --version
21              Output the version number.
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23       -o, --out file
24              Specify  the  output TopoJSON file name.  Defaults to - for std‐
25              out.
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27       -k, --key expression
28              Specify a JavaScript expression, given a TopoJSON  geometry  ob‐
29              ject d and its zero-based index i in its parent collection, that
30              determines how geometry objects are grouped before merging; each
31              group  is  merged  separately.  For example, given a topology of
32              U.S. counties, where the id of each  county  is  its  five-digit
33              FIPS code, the county boundaries can be merged into state bound‐
34              aries by using the first two digits of  the  county  FIPS  code,
35              which represents the state FIPS code:
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37                  topomerge states=counties -k 'd.id.slice(0, 2)' < us-counties.json > us-states.json
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39              If  a  key  is not specified, all input geometry objects will be
40              merged together.  For example, this can be  used  to  merge  the
41              state boundaries into a single nation boundary:
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43                  topomerge nation=states < us-states.json > us.json
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45       -f, --filter expression
46              Specify  a  JavaScript  expression that filters the input geome‐
47              tries before merging or meshing.  In  conjunction  with  --mesh,
48              the  expression  is  given two TopoJSON geometry objects a and b
49              that represent the adjacent features for a given arc segment; if
50              the expression evaluates truthily, the associated arc segment is
51              retained in mesh.  Otherwise, the expression is given  an  input
52              TopoJSON  geometry  object  d  and its zero-based index i in its
53              parent collection; if the expression evaluates truthily, the ge‐
54              ometry object is retained in the merged polygon.
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56       --mesh Generate a geometry collection of lines rather than polygons.
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SEE ALSO

59       geo2topo(1), topo2geo(1), topoquantize(1), toposimplify(1)
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63                                 January 2021                     TOPOMERGE(1)
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