Loop for forward difference finite method

Question

Richard Rees 2019-7-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/473505-loop-for-forward-difference-finite-method

评论： Richard Rees 2019-7-30

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

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Stephen23 2019-7-26

编辑：Stephen23 2019-7-26

在 MATLAB Online 中打开

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 2019-7-26