I want to plot a contourf (or imshow) map with some scatter symbol lay on it, and I
want them to use a same color set.
like contour(x,y,z) or imshow(x,y,z) have a color set (colorbar)
and scatter(x1,y1, s=z1,c=z1). in the scatter, the color of z1 would be the same with
the color of z if their value is the same. How could I do? thanks!