error >> Matrix dimensions must agree. How to fix

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??

Answer 1

[Anjaneyulu Bairi]

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

https://in.mathworks.com/help/matlab/learn_matlab/matrices-and-arrays.html

https://www.mathworks.com/help/matlab/matlab_prog/compatible-array-sizes-for-basic-operations.html

I hope above information is helpful to resolve your query

Answer 2

[Lokesh]

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:

https://www.mathworks.com/help/matlab/matlab_prog/compatible-array-sizes-for-basic-operations.html

Hope this helps!

Answer 3

[Torsten]

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)])