
plvect: Vector plot 

DESCRIPTION:

    This function is used in example 22. 

SYNOPSIS:

plvect(u, v, nx, ny, scale, pltr, pltr_data)

ARGUMENTS:

    u, v (const PLFLT * const *, input) :    Pointers to a pair of
    vectored two-dimensional arrays containing the x and y components
    of the vector data to be plotted. 

    nx, ny (PLINT, input) :    Physical dimensions of the arrays u and v. 

    scale (PLFLT, input) :    Parameter to control the scaling factor of
    the vectors for plotting. If scale = 0 then the scaling factor is
    automatically calculated for the data. If scale < 0 then the
    scaling factor is automatically calculated for the data and then
    multiplied by -
    scale. If scale > 0 then the scaling factor is set to scale. 

    pltr (void (*) (PLFLT, PLFLT, PLFLT *, PLFLT *, PLPointer) , input) : 
      Pointer to function that defines transformation between indices
    in array z and the world coordinates (C only).    Transformation
    functions are provided in the PLplot library: pltr0 for identity
    mapping, and pltr1 and pltr2 for arbitrary mappings respectively
    defined by one- and two-dimensional arrays.  In addition,
    user-supplied routines for the transformation can be used as well.
     Examples of all of these approaches are given in the PLplot
    documentation. The transformation function should have the form
    given by any of pltr0, pltr1, or pltr2. 

    pltr_data (PLPointer, input) :    Extra parameter to help pass
    information to pltr0, pltr1, pltr2, or whatever routine that is
    externally supplied. 
