6 hump camel function - What is wrong with the code?

Hello,

I am trying to plot the 6 hump camel back function using a simple code as shown below:

[x,y]=meshgrid(-2:0.02:2,-1:0.01:1);
z=((4-(2.1*(x.^2))+((x.^4)/3))*(x.^2))+(x.*y.*1)+(4*(-1+(y.^2))*(y.^2));
mesh(x,y,z)

A plot is made but it does not match the actual function at all. The term (x.*y.*1) was written so since an error was observed when I dropped the *1 (Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.). How do I correct this?

Answer 1

[Guillaume]

The overuse of unnecessary brackets and the lack of any spacing make your expression very hard to read.

Multiplying by 1 will never change the result and will never make any difference to any error.

Your expression, without all the unnecessary brackets and with some spacing:

z = (4 - 2.1*x.^2 + x.^4/3)*x.^2 + x.*y + 4*(-1 + y.^2)*y.^2;

In my opinion much easier to read, and you can immediately see the two errors. You're doing matrix multiplication with x.^2 and y.^2 instead of element-wise multiplication. Changing the two * into .* is probably what you want:

z = (4 - 2.1*x.^2 + x.^4/3).*x.^2 + x.*y + 4*(-1 + y.^2).*y.^2;

[Mohammed Muaaz Hussain]

Thank you very much :)