change nested for to vectorise

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

Answer 1

[David Sanchez]

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

[Mani Ahmadian]

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

Answer 2

[Mani Ahmadian]

Hi everybody.

would you please help me to improve my code?

Thanks a lot.

Mani