Adding values of Columns in a matrix to create another matrix (for loop)

I have a 442x25 matrix 'yield' which I want to sum each column in 'yield' to create a 1x25 matrix 'nyi', so this can be multiplied by another 1x25 matrix Np.

I ran this exact code earlier on a different computer where both of the matrices were produced the size they are meant to be so i am not sure what is wrong.

It seems as if the code thinks there are only two columns.? But I have 25 columns

I am an amateur when it comes to matlab so I would really appreciate any help!

See the code for my loop and errors produced:

dim=size(E_min,2);

fun = @(E) A*exp(-E/kT);

for i = 1:dim        
     
    
    Np=integral(fun,E_min(i), E_max(i));
    Np(i)=Np;
    
    y=yield(:,1:i,1);
    nyi=sum(y);
    
    num(:,i)=nyi*Np(i);

end

The code is recognising my dim as 1x25 (which is correct) however when I run the following loop I am getting an error

Unable to perform assignment because the size of the left side is 1-by-1 and

the size of the right side is 1-by-2

Error in matrixfunction (line 41)

num(:,i)=nyi*Np(i);

Answer 1

[Ridwan Alam]

dim=size(E_min,2);
% dim = 25

fun = @(E) A*exp(-E/kT);

Np = []; 
nyi = []; 
for i = 1:dim    
    
    Np(i)=integral(fun,E_min(i), E_max(i));
    % size(Np) is 1x25 
        
    % size(yield) is 442 x 25
    y=yield(:,i); % size(y) is 442 x 1
    
    nyi(i)=sum(y); % size(nyi) is 1x25
    
end

num = nyi .* Np; % size(num) is 1x25

Hope this helps!

[Anna B]

I have tried this and the same thing is being produced.

It seems to be treating i as 1 and not as a loop?

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 442-by-1.

Error in matrixfunction (line 41)

num(:,i)=nyi*Np(i);

[Anna B]

I have 2 (1x25) matrices names E_min and E_max, I am integrating with boundaries E_min(1) and E_max(1), then E_min(2) and so on to create a matrix of 1x25 for Np. It is instead giving me a 1x1 value.

[Anna B]

I want Np to be a matrix 1x25, how can I do this? so that i get the integrated values for each E_min E_max in one row

I also want yield to be a matrix of 442x25, where each column is then sum to give a 1x25 matrix (nyi)

Num is then just multiplying the values of Np(if Np were a 1x25) and nyi(if it were a 1x25 matrix)

Hope that makes sense.

[Ridwan Alam]

The answer above is updated. Please check!

[Anna B]

This works perfect!! Thank you so much for your help!

[Ridwan Alam]

Sure. Glad to help.

Answer 2

[Allen]

Anna, if you are trying to multiple two 1x25 vectors element-wise then try using a period in front of the multiplication operator.

% Two 1x25 vectors with random values
Np = rand([1,25]);
nyi = rand([1,25]);

% Use '.*' for element-wise calculations instead of '*' which is trying to perform dot-multiplication.
% For '*' to work with two vectors they would need to be sized 1xn and nx1.
Np.*nyi