MATLAB: How to execute the loop at a relatively short time

loops

It is taking like forever (over 6 hours) to execute a loop. The size of my variables are;

Z = 2041211 element

Distance = 2021×2021 double

    for duidx = 1:Z
        Summation_Residual_Squared(duidx) = sum(Residual_Squared(Distance_Unique(duidx)==Distance));
        Semivariance(duidx) = Summation_Residual_Squared(duidx)/(2*sum(Distance(:)== Distance_Unique(duidx)));
    end

Am I working with large files such that the execution time I'm obtaining is normal or is there something i'm missing.

Thanks.

Darl.

Best Answer

Distance -> D

Distance_Unique -> DU

Residual_Squared -> RS

Summation_Residual_Squared -> SRS

Semivariance -> S

DD = D(:);
[lo,ii] = ismember(DD,DU);
SRS = accumarray(ii(lo),RS(lo));
S = SRS./accumarray(ii(lo),1);

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MATLAB: How can i make the code run faster

Assuming Distance_Unique, Distance, etc. are all matrices or vectors and not functions, the two inner loops are certainly not required. I also assumed you've predeclared your Summation_Residual_Squared vector to avoid growing it in the loop.

Summation_Residual_Squared = zeros(size(Distance_Unique));
for duidx = 1:numel(Distance_Unique)
   Residual_Sqrd = Residual_Squared(Distance_Unique(duidx) == Distance);
   Summation_Residual_Squared(duidx) = sum(Residual_Sqrd(:));
end

MATLAB: How to find nearby labels

I =[...
     1     1     1     2     3     3
     1     1     2     2     3     3
     4     4     4     5     5     3
     4     4     4     4     5     5];
 
N = unique(I);
n = numel(N);
out = cell(n,2);
for ii = 1:n
    out(ii,:) = {ii, unique(I(bwdist(I == ii,'chessboard')==1))};
end

N = unique(I);
n = numel(N);
out = cell(n,2);
o3 = ones(3);
for ii = 1:n
    lo = I == ii;
    out(ii,:) = {ii, unique(I(imdilate(lo,o3) + lo == 1))};
end
out_as_table = cell2table(out,'v',{'number','neighbours'})

Best Answer

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