
plmeridians: Plot latitude and longitude lines 

DESCRIPTION:

    This function is used in example 19. 

SYNOPSIS:

plmeridians(mapform, dlong, dlat, minlong, maxlong, minlat, maxlat)

ARGUMENTS:

    mapform (void (*) (PLINT, PLFLT *, PLFLT *), input) :    A user
    supplied function to transform the coordinate  longitudes and
    latitudes to a plot coordinate system.     By using this transform,
    we can change from a longitude,  latitude coordinate to a polar
    stereographic project, for  example.  Initially, x[0]..[n-1] are
    the longitudes and y[0]..y[n-1]  are the corresponding latitudes. 
    After the call to mapform(), x[]  and y[] should be replaced by
    the corresponding plot coordinates.   If no transform is desired,
    mapform can be replaced by NULL. 

    dlong (PLFLT, input) :    The interval in degrees at which the
    longitude lines are to be plotted. 

    dlat (PLFLT, input) :    The interval in degrees at which the latitude
    lines are to be plotted. 

    minlong (PLFLT, input) :    The value of the longitude on the left
    side of the plot.  The value of minlong must be less than the
    value of maxlong, and the  quantity maxlong-minlong must be less
    than or equal to 360. 

    maxlong (PLFLT, input) :    The value of the longitude on the right
    side of the plot. 

    minlat (PLFLT, input) :    The minimum latitude to be plotted on the
    background.   One can always use -90.0 as the boundary outside the
    plot window  will be automatically eliminated.    However, the
    program will be  faster if one can reduce the size of the
    background plotted. 

    maxlat (PLFLT, input) :    The maximum latitudes to be plotted on the
    background.   One can always use 90.0 as the boundary outside the
    plot window  will be automatically eliminated. 
