csinterpxy(x, y, rate)
{
        local olen, erate;

        if (argc < 3)
        {
                if (argc < 2) error(sprintf("%s - input series required", __FUNC__));

                rate = rate(y);
        }

        if (isdtunit(getvunits(x)))
        {
                /* dt */
                sethunits(y, getvunits(x));
        }

        /* expected output length */
        olen = 1 + round((max(x) - min(x)) * rate);

        /* effective sample rate assuming input rate of 1.0 */
        erate = (olen - 1) / (length(y) - 1);

        /* csinterp y vals */
        y = csinterp(y, rate(y) * erate);

        /* linearly interp x vals */
        x = xyinterp(x, deltax(x) / erate);

        /* linearly sample */
        y = xyinterp(x, y, 1.0 / rate);

        return(y);
}