PLGRIDDATA(3)                     PLplot API                     PLGRIDDATA(3)



NAME
       plgriddata - Grid data from irregularly sampled data

SYNOPSIS
       plggriddata(x, y, z, npts, xg, nptsx, yg, nptsy, zg, type, data)

DESCRIPTION
       Real world data is frequently irregularly sampled, but all PLplot 3D
       plots require data placed in a uniform grid. This function takes
       irregularly sampled data from three input arrays x[npts], y[npts], and
       z[npts], reads the desired grid location from input arrays xg[nptsx]
       and yg[nptsy], and returns the gridded data into output array
       zg[nptsx][nptsy].  The algorithm used to grid the data is specified
       with the argument type which can have one parameter specified in
       argument data.

       Redacted form:  General: plgriddata(x, y, z, xg, yg, zg, type, data)
       Perl/PDL: Not available?


       This function is used in examples 1,14.

ARGUMENTS
       x (PLFLT *, input)
              The input x array.

       y (PLFLT *, input)
              The input y array.

       z (PLFLT *, input)
              The input z array. Each triple x[i], y[i], z[i] represents one
              data sample coordinate.

       npts (PLINT, input)
              The number of data samples in the x, y and z arrays.

       xg (PLFLT *, input)
              The input array that specifies the grid spacing in the x
              direction. Usually xg has nptsx equally spaced values from the
              minimum to the maximum values of the x input array.

       nptsx (PLINT, input)
              The number of points in the xg array.

       yg (PLFLT *, input)
              The input array that specifies the grid spacing in the y
              direction. Similar to the xg parameter.

       nptsy (PLINT, input)
              The number of points in the yg array.

       zg (PLFLT **, output)
              The output array, where data lies in the regular grid specified
              by xg and yg. the zg array must exist or be allocated by the
              user prior to the call, and must have dimension
              zg[nptsx][nptsy].

       type (PLINT, input)
              The type of gridding algorithm to use, which can be: GRID_CSA:
              Bivariate Cubic Spline approximation GRID_DTLI: Delaunay
              Triangulation Linear Interpolation GRID_NNI: Natural Neighbors
              Interpolation GRID_NNIDW: Nearest Neighbors Inverse Distance
              Weighted GRID_NNLI: Nearest Neighbors Linear Interpolation
              GRID_NNAIDW:  Nearest Neighbors Around Inverse Distance Weighted
              For details of the algorithms read the source file plgridd.c.

       data (PLFLT, input)
              Some gridding algorithms require extra data, which can be
              specified through this argument. Currently, for algorithm:
              GRID_NNIDW, data specifies the number of neighbors to use, the
              lower the value, the noisier (more local) the approximation is.
              GRID_NNLI, data specifies what a thin triangle is, in the range
              [1. .. 2.]. High values enable the usage of very thin triangles
              for interpolation, possibly resulting in error in the
              approximation.  GRID_NNI, only weights greater than data will be
              accepted. If 0, all weights will be accepted.



AUTHORS
       Geoffrey Furnish and Maurice LeBrun wrote and maintain PLplot.  This
       man page was automatically generated from the DocBook source of the
       PLplot documentation, maintained by Alan W. Irwin and Rafael
       Laboissiere.

SEE ALSO
       PLplot documentation at http://plplot.sourceforge.net/resources.



                                November, 2007                   PLGRIDDATA(3)
