在Matlab中绘制3-D图形和水平曲线

Question

I have the following code below, but I cannot test it since I do not have Matlab with me right now and I am afraid I might not have the time to test it by myself when I finally get it. I'm trying to plot both 3-d graphs and graphs of the level curves in the y and x axis (two dimensions only) of three different types of functions. I would appreciate if someone could point if there is something wrong with the code below.

**************************************************************
**plotting functions -- level curves and 3d graph** 

x_val = linspace(0, 100, 200); 
y_val = linspace(0, 100, 200); 
[x, y] = meshgrid(x_val, y_val); 
z = ln(x).+y.;  
figure 
contour3(y, x, z)
contour(y, x, z)


********************************

z = (x.^1/2)+y.;  
figure 
contour3(y, x, z)
contour(y, x, z)

*********************************


z = (x.^1/3)+y.; 
figure 
contour3(y, x, z)
contour(y, x, z)

Answer 1

ln is not a valid matlab symbol, in addition to the excess of dots mentioned and comment formatting above. The following runs on Matlab.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%plotting functions -- level curves and 3d graph%% 

x_val = linspace(0, 100, 200); 
y_val = linspace(0, 100, 200); 
[x, y] = meshgrid(x_val, y_val); 
z = log(x)+y;  
figure 
contour3(y, x, z)
figure 
contour(y, x, z)


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

z = (x.^1/2)+y;  
figure 
contour3(y, x, z)
figure 
contour(y, x, z)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


z = (x^1/3)+y; 
figure 
contour3(y, x, z)
figure 
contour(y, x, z)

Answer 2

For starters, comments in MATLAB are "%" not "*".

You have a few mistakes, trying to do element-wise operators, I think.

Your three assignments of z have too many dots:

 z = log(x)+y;  
 z = (x.^1/2)+y; 
 z = (x.^1/3)+y; 

It is not necessary to use ".+", because MATLAB automatically adds matrices elementwise.