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tabpolygon - select points from a table that are either inside or outside
a polygon
tabpolygon [parameter=value]
tabpolygon uses
two columns from a table as the X and Y coordinates of a series of points
in a plane, and allows you to define a polygon in that coordinate system
and output only lines whose points would lie either inside or outside that
polygon.
Optionally rejected lines can be output as comments, which keeps
the linecount of input and output the same.
The following parameters
are recognized in any order if the keyword is also given:
- in=
- Input file
name (table). No default
- xcol=
- X coordinate column [1]
- ycol=
- Y coordinate
column [2]
- polygon=
- The (minimum 3) pairs of X,Y that define the polygon.
These must be in the same coordinate system as the one in the X and Y columns,
and the last point is automatically closed connected to the first point
to close the polygon. There is no check for self-intersecting polygons
such as the figure 8. No default.
- inside=
- Select inside of region to be
output? [t]
- comment=
- Also copy comment lines?. If true, comment lines, as
well as points failing to match the inside/outside polygon criterion, will
be output, but commented using the usual # symbol.. Default : f
Here
is how points in two (assumed disjoint) regions are identified, and the
remnant in the 3rd table.
% tabpolygon in=points_all.tab polygon=@region1.pol > points_1.tab
% tabpolygon in=points_all.tab polygon=@region1.pol inside=f > points_not_1.tab
% tabpolygon in=points_not_1.tab polygon=@region2.pol > points_2.tab
% tabpolygon in=points_not_1.tab polygon=@region2.pol inside=f > points_3.tab
Boolean operations on multiple regions is cumbersome or impossible
at the moment.
tabmath(1NEMO)
src/kernel/tab/tabpolygon.c source
code
Peter Teuben
05-Mar-13 V0.1 Created PJT
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