# error >> Matrix dimensions must agree. How to fix

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Ofer Aluf on 23 Apr 2024
Edited: Torsten on 23 Apr 2024
Hello,
I have script:
d=0.025:0.0025:1; % d=0.125*Lambda to 12.5*Lambda
Lambda=1;
% Ga function
Lambda=0.2;l1= Lambda/4;zi=l1;si=1;k=(2*pi)/Lambda;
z=0:Lambda/400:Lambda/4;
y= sqrt(d.^2+(z-zi));
Arrays have incompatible sizes for this operation.
Gfun=@(z)(1./y).*exp(-1i.*k.*y).*exp(-1i.*k.*si.*z);
% R=sqrt(d^2+(z-zi));
% evaluate the integral from z=0 to l1
Ga=integral(Gfun,0,Lambda/4);
Question? Why i got message "Matrix dimensions must agree"? and how to fix it??
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### Answers (3)

Anjaneyulu Bairi on 23 Apr 2024
Edited: Anjaneyulu Bairi on 23 Apr 2024
Hi,
Below line causing the error and it says "z" and "zi" are incompatible sizes for this operation.
y= sqrt(d.^2+(z-zi));
The "d.^2" variable has size of 1*391 double and "(z-zi)" has size of 1*101 double. Make sure you have declared these variables correctly to avoid these kind of errors.
You can refer below documentation links to know more information on arrays
I hope above information is helpful to resolve your query
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Lokesh on 23 Apr 2024
Hi Ofer,
It appears that you are encountering the error "Matrix dimensions must agree" while running your MATLAB script.
This issue arises because the dimensions of "d.^2" (1x391) and "z-zi" (1x101) in the equation "y= sqrt(d.^2+(z-zi));" are not compatible, leading to the error.
Please refer to the following MATLAB documentation for more information about compatible array sizes for basic operations:
Hope this helps!
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Torsten on 23 Apr 2024
Edited: Torsten on 23 Apr 2024
z doesn't need to be prescribed in array form because you integrate with respect to z. Here I assume that the integration variable and the z in the expression for y are the same.
If you mean to evaluate your integral for the d-values that you defined, you can use
d=0.025:0.0025:1; % d=0.125*Lambda to 12.5*Lambda
% Ga function
Lambda=0.2;l1=Lambda/4;zi=l1;si=1;k=(2*pi)/Lambda;
y= @(d,z)sqrt(d^2+(z-zi));
Gfun =@(d,z)(1./y(d,z)).*exp(-1i.*k.*y(d,z)).*exp(-1i.*k.*si.*z);
Ga=arrayfun(@(d)integral(@(z)Gfun(d,z),0,Lambda/4),d);
plot(d,[real(Ga);imag(Ga)])
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