zinterpxy(x, y, rate)
{
        local xmin, xmax;

        /* zinterp y vals */
        y = zinterp(y, rate);

        /* linearly interp x vals */
        (xmin, xmax) = xminmax(x);

        x = xylookup(x, linspace(xmin, xmax, length(y)));

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

        return(y);
}