MATLAB: Loop through gridded data

dimensionerrorgridloop

I wrote this code using Matlab R2014a in order to loop through a virtual grid:
clear, clc
format long g
load rN_Tang.txt
load aN_Tang.txt
c=aN_Tang(:,:); 
f=rN_Tang(:,:);
DepthsA=-c(:,3);
LongitudeA=c(:,1);
DepthsR=-f(:,3);
LongitudeR=f(:,1);
for I=724:747;
  J=2:8;
  k=1:length(aN_Tang);
  l=1:length(rN_Tang);
  if ((I<LongitudeA(k)<=I+1 & J<DepthsA(k)<=J+1) & ...
      (I<LongitudeR(l)<=I+1 & J<DepthsR(l)<=J+1))
    if (isempty(DepthsA(k))==0 & isempty(DepthsR(l))==1)
      Zmoy(I,J)=min(DepthsA(k));
    elseif (isempty(DepthsA(k))==1 & isempty(DepthsR(l))==0)
      Zmoy(I,J)=min(DepthsR(l));
    elseif (isempty(DepthsA(k))==1 & isempty(DepthsR(l))==1)
      %Ne rien faire, i.e "Void"
    elseif (isempty(DepthsA(k))==0 & isempty(DepthsR(l))==0)
      zAmin(I,J)=min(DepthsA(k));
      DZ(I,J)=min(abs(zAmin(I,J)-DepthsR(l)));
      if zAmin(I,J)<=DepthsR(l)
        zRmin(I,J)=zAmin(I,J)+DZ(I,J);
      else 
        zRmin(I,J)=zAmin(I,J)-DZ(I,J);
      end
      Zmoy(I,J)=(zAmin(I,J)+zRmin(I,J))/2;
    end
  end
  Zm=-1*mean(Zmoy(I,J))
end
Matlab response :"
Error using < Matrix dimensions must agree.
Error in plN_Tang (line 60) 
if ((I<LongitudeA(k)<=I+1 & J<DepthsA(k)<=J+1) & (I<LongitudeR(l)<=I+1 & J<DepthsR(l)<=J+1))"
What's wrong with the loop?
PS:I'd be so grateful if someone has an idea about this issue!

Best Answer

...
for I=724:747;
  J=2:8;
  k=1:length(aN_Tang);
  l=1:length(rN_Tang);
  if ((I<LongitudeA(k)<=I+1 & J<DepthsA(k)<=J+1) & ...
      (I<LongitudeR(l)<=I+1 & J<DepthsR(l)<=J+1))
    ...
J, k, and l are invariant and so should be outside the loop...
J=2:8;
k=1:length(aN_Tang);
l=1:length(rN_Tang);
for I=724:747;
  if ((I<LongitudeA(k)<=I+1 & J<DepthsA(k)<=J+1) & ...
      (I<LongitudeR(l)<=I+1 & J<DepthsR(l)<=J+1))
    ...
Now I is a single value and while k is a vector of some unknown length but thus the returned subarray LongitudeA(k) is also of that length (presuming the size of the array is commensurate with that and the values are within the array bounds). But, you have a disparate size between a single value I and a vector LongitudeA(k) which causes a Matlab failure. Similar problems occur with the other arrays.
Not precisely sure what you're really after here so not positive the right coding solution...
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