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change nested for to vectorise

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Mani Ahmadian
Mani Ahmadian el 22 de Oct. de 2014
Cerrada: MATLAB Answer Bot el 20 de Ag. de 2021
Hi
I have a 100*100 grid as below:
xgrid=1:100;
ygrid=1:100;
I have 5 data points in this grid(x,y) as below,too:
X=[10 20 30 40 50];
Y=[55 65 75 85 95];
to compute distances of each node from these data points,I use a nested for structure as:
deltaX=zeros(100,100,length(X));
deltaY=zeros(100,100,length(X));
for ii=1:length(X)
for jj=1:100
for kk=1:100
deltaX(jj,kk,ii)=X(ii)-xgrid(kk);
deltaY(jj,kk,ii)=Y(ii)-ygrid(kk);
end
end
end
deltaY=permute(deltaY,[2 1 3]);
distance1=hypot(deltaX,deltaY);
distancegrid=zeros(100,100,length(X));
distancegrid=squeeze(distance1);
I want to remove this nested for structure and vectorise my code. How it's possible to do?
Thanks a lot
Mani

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Respuestas (2)

David Sanchez
David Sanchez el 22 de Oct. de 2014
xgrid=1:100;
ygrid=1:100;
X=[10 20 30 40 50];
Y=[55 65 75 85 95];
% to start with, there is no need of a 3D matrix.
% you result is the same along your jj dimension
deltaX=zeros(100,length(X));
deltaY=zeros(100,length(X));
% and you can vectorize like this
for ii=1:length(X)
deltaX(:,ii)=X(ii)-xgrid;
deltaY(:,ii)=Y(ii)-ygrid;
end
  1 comentario
Mani Ahmadian
Mani Ahmadian el 22 de Oct. de 2014
Dear David
Thanks for your answer. But I'm trying to find a way to do all computations without for structure, I have limitations because my data base is very large and it's so time consuming. Do you/someone have an approach to do the job without for structure?
Mani
Mani Ahmadian
Mani Ahmadian el 22 de Oct. de 2014
Hi everybody.
would you please help me to improve my code?
Thanks a lot.
Mani

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