Loop for forward difference finite method

Good evening everyone,

I have a problem whereby my function stops running at the end of first row and doesn't start up again at the beginning of the next because I do not know to tell it that it has reached the end.

d_d = diff(dd,1,2);
ts = 1440;
 % Finds the dimensions of the matrix containing PWP values for each node
sPWP = d_d(:,:);% Starts at the beginning value for each column 
sPWP = [d_d, d_d(:,end)]; % Duplicate the end row 
[rows, zones] = size(d_d);
    

dfdx_sim = nan(size(sPWP)); %Preallocate zero matrix based on B dimensions (Saves the CPU reiterating over the same list) 

for g = 1:zones
    for h = 1:rows
        %while g+1<zones 
        dfdx_sim(g,h) = ((sPWP(g+1,h) - sPWP(g,h)))/ts;
        %continue
    end           
end

Thanks

[Stephen23]

When I load your .mat file and run your code I get this error:

Undefined function or variable 'dd'.
Error in sample (line 5)
d_d = diff(dd,1,2);

When I comment-out that line (because you seem to have supplied d_d in the .mat file) I get this error:

Attempted to access sPWP(2,8); index out of bounds because size(sPWP)=[191,7].
Error in sample (line 16)
        dfdx_sim(g,h) = ((sPWP(g+1,h) - sPWP(g,h)))/ts; 

Please ensure that your code and data demonstrate what you experience. It we cannot reproduce what you are experiencing, then it makes it harder for us to help you.

[Richard Rees]

Good morning, I have uploaded an excel file with the data on.

Thanks

Answer 1

[SaiDileep Kola]

I went through your code and I see that you need to swap the arguments “g” and “h” in the equation inside the nested “for” loop

dfdx_sim(h,g) = ((sPWP(h,g+1) - sPWP(h,g)))/ts;

You will get the expected output now.

[Richard Rees]

Hi, thanks for that. I figured out the same thing.