- Added a lot of "dot''s to the line of code in your loop. When you have vectors, and you want to do operation on those vectors element-by-element, you need to add those dots, so that MATLAB does not think you want to do matrix operations (e.g. matrix multiply or matrix inverse).
- Added the line "e = exp(1)" to your code. MATLAB does not have "e" predefined. You could also have used the exp() function instead of your syntax.

# Mexican Hat function plot help

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Hello all,

I'm trying to plot a certain Mexican Hat function (other than the one they provide in MATLAB), but I'm getting the matrix dimensions must agree when I define psi. I tried everything to fix the code, but no luck. Can someone advise?

I know some code is repetitive, but I need them in other areas of my code.

dXs = 1;

x = [-20,20];

SamplingScale = [1, dXs, 4, 20 ,40];

Range = SamplingScale;

HalfRange = Range/2;

Sigma = HalfRange/4;

SigmaSq = Sigma.^2;

for i = 1:length(x)

psi = (2/(sqrt(3)*Sigma)*pi^(-0.25))*(1-(i^2/Sigma^2))*(e^(-i^2/2*SigmaSq));

end

plot (psi)

Thanks again!

##### 0 Comments

### Accepted Answer

the cyclist
on 5 Oct 2011

I did two main things with your code (pasted below):

You might want to read the "Getting Started" guide: http://www.mathworks.com/help/techdoc/learn_matlab/bqr_2pl.html

dXs = 1;

x = [-20,20];

SamplingScale = [1, dXs, 4, 20 ,40];

Range = SamplingScale;

HalfRange = Range/2;

Sigma = HalfRange/4;

SigmaSq = Sigma.^2;

e = exp(1);

for i = 1:length(x)

psi = (2./(sqrt(3)*Sigma)*pi^(-0.25)).*(1-(i^2./(Sigma.^2))).*(e.^(-i^2./(2*SigmaSq)));

end

plot (psi)

### More Answers (1)

Palguna Gopireddy
on 31 Mar 2022

What is the mexihat equation used in matlab. In original equation there is no term called [lb,ub].

##### 3 Comments

Palguna Gopireddy
on 8 Apr 2022

Thanks.Got it.any function can be know seen by pressing right click on it and opening it.

But for chebwin function one of the lines is 'chebwinx' which can't be opened. They said it is a MEX file. Do you know any way to open and see a MEX file in matlab.

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