/* build column or row shade data */
shader(w, byrow)
{
        if (argc < 2)
        {
                if (argc < 1) return;
                
                byrow = 0;
        }

        if (getwnum(w) == getwnum(w0)) return;

        /* create a uniform shade list */
        if (byrow)
        {
                /* each row same color */
                list = repmat(1..length(w), 1, numcols(w));
        }
        else
        {
                /* each col same color */
                list = ones(length(w), numcols(w)) * ((1..numcols(w))');
        }
        if (outargc < 1)
        {
                curwin = refwindow(w0);

                /* put shade data in current window */
                list;

                /* shade target with shade data */
                shadewith(w, curwin);

                /* show it */
                plotmode(w, 1);
        }
        else
        {
                /* just return data */
                return(list);
        }
}