remove nested for structure

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

[Matt J]

X=reshape(X,1,1,[]);
Y=reshape(Y,1,1,[]);

xgrid=linspace(xmin,xmax,100);
ygrid=linspace(ymin,ymax,100);

delta = hypot(   bsxfun(@minus,X,xgrid)   ,  bsxfun(@minus,Y,ygrid));

No idea why you've applied repmat along the jj-axis. It just duplicates data with no apparent purpose. But, you can incorporate it with the above, if you like

    delta= repmat(delta,100,1);