1PLMAP(3plplot)                    PLplot API                    PLMAP(3plplot)
2
3
4

NAME

6       plmap - Plot continental outline or shapefile data in world coordinates
7

SYNOPSIS

9       plmap(mapform, name, minx, maxx, miny, maxy)
10

DESCRIPTION

12       Plots  continental  outlines  or shapefile data in world coordinates. A
13       demonstration of how to use this function to create  different  projec‐
14       tions  can  be  found in examples/c/x19c. PLplot is provided with basic
15       coastal outlines and USA state borders. To use  the  map  functionality
16       PLplot  must be compiled with the shapelib library. Shapefiles have be‐
17       come a popular standard for geographical data and data in  this  format
18       can  be easily found from a number of online sources. Shapefile data is
19       actually provided as three or more files with the  same  filename,  but
20       different extensions. The .shp and .shx files are required for plotting
21       Shapefile data with PLplot.
22
23       PLplot currently supports the point, multipoint, polyline  and  polygon
24       objects within shapefiles. However holes in polygons are not supported.
25       When plmap is used the type of object is derived from the shapefile, if
26       you wish to override the type then use one of the other plmap variants.
27       The built in maps have line data only.
28
29       Redacted form: plmap(mapform, name, minx, maxx, miny, maxy)
30
31       This function is used in example 19.
32

ARGUMENTS

34       mapform (PLMAPFORM_callback(3plplot), input)
35              A user supplied function to transform the original map data  co‐
36              ordinates  to  a  new coordinate system. The PLplot-supplied map
37              data is provided as latitudes and  longitudes;  other  Shapefile
38              data may be provided in other coordinate systems as can be found
39              in their .prj plain text  files.  For  example,  by  using  this
40              transform we can change from a longitude, latitude coordinate to
41              a polar stereographic projection. Initially, x[0]..[n-1] are the
42              original x coordinates (longitudes for the PLplot-supplied data)
43              and y[0]..y[n-1] are the corresponding y coordinates  (latitudes
44              for the PLplot supplied data).  After the call to mapform(), x[]
45              and y[] should be replaced by  the  corresponding  plot  coordi‐
46              nates.  If  no  transform is desired, mapform can be replaced by
47              NULL.
48
49       name (PLCHAR_VECTOR(3plplot), input)
50              An ascii character string specifying the type  of  map  plotted.
51              This  is either one of the PLplot built-in maps or the file name
52              of a set of Shapefile files without the file extensions. For the
53              PLplot  built-in maps the possible values are: "globe" -- conti‐
54              nental outlines "usa" -- USA and state  boundaries  "cglobe"  --
55              continental  outlines  and  countries  "usaglobe"  -- USA, state
56              boundaries and continental outlines
57
58
59       minx (PLFLT(3plplot), input)
60              The minimum x value of map elements to be drawn. The units  must
61              match the shapefile (built in maps are degrees lat/lon). Objects
62              in the file which do not encroach on the box  defined  by  minx,
63              maxx,  miny,  maxy will not be rendered. But note this is simply
64              an optimisation, not a clipping so for objects with some  points
65              inside  the  box  and some points outside the box all the points
66              will be rendered. These parameters also define latitude and lon‐
67              gitude  wrapping  for  shapefiles  using  these units. Longitude
68              points will be wrapped by integer multiples of  360  degrees  to
69              place  them  in the box. This allows the same data to be used on
70              plots from -180-180 or 0-360 longitude ranges. In  fact  if  you
71              plot  from  -180-540  you will get two cycles of data drawn. The
72              value of minx must be less than the value of maxx. Passing in  a
73              nan, max/-max floating point number or +/-infinity will case the
74              bounding box from the shapefile to be used.
75
76       maxx (PLFLT(3plplot), input)
77              The maximum x value of map elements to be drawn - see minx.
78
79       miny (PLFLT(3plplot), input)
80              The minimum y value of map elements to be drawn - see minx.
81
82       maxy (PLFLT(3plplot), input)
83              The maximum y value of map elements to be drawn - see minx.
84
85

AUTHORS

87       Many developers (who  are  credited  at  http://plplot.org/credits.php)
88       have contributed to PLplot over its long history.
89

SEE ALSO

91       PLplot documentation at http://plplot.org/documentation.php.
92
93
94
95                                 January, 2023                  PLMAP(3plplot)
Impressum