
plstransform: Set a global coordinate transform function 

DESCRIPTION:

    This function is used in examples 19 and 22. 

SYNOPSIS:

plstransform(coordinate_transform, coordinate_transform_data)

ARGUMENTS:

    coordinate_transform (void (*) (PLFLT, PLFLT, PLFLT *, PLFLT *,
    PLPointer) , input) :     Pointer to a function that defines a
    transformation from the input (x, y) coordinate to a new plot
    world coordinate. A NULL pointer  means that no transform is
    applied. 

    coordinate_transform_data (PLPointer, input) :    Optional extra data
    for 
    coordinate_transform. 
