matlab绘图 就是绘图的时候，如果我们想挖掉一部分，那么nan就起作用了比如我们要绘制z=x^2+y^2在[-1010]区域的图形但是要挖掉x(Matlab drawing When we're drawing, Nan works if we want to dig out a part of it. For example, we're going to plot the z=x^2+y^2 in the [-1010] region, but dig out the