MATLAB: How we write condition in for loop

matlab coder

suppose in c language we have a condition like k=0;k<j;k++

how we write this code in matlab?

Best Answer

k=0;

while k<j

k=k+1

end

Related Solutions

MATLAB: For loop with multiple variables

If you want this:

Java: for (int i = 1, j = 0; i <= limit; i++, j++)

in Matlab:

j = 0;
for i = 1:limit
  j = j + 1;
  ...
end

Less nice alternatives:

index = [1:limit; ...
         1:limit];
for k = 1:size(index, 2)
   i = index(1, k);
   j = index(2, k);
   ...
end

index = [1:limit; ...
         1:limit];
for k = index
   i = k(1);
   j = k(2);
   ...
end

The last one might look strange. The FOR loop evaluates the given index vector along the 2nd dimension, such that the column vectors are assigned to k.

Maybe this is useful for you:

indexI = 1:limit;
indexJ = 1:limit;  % Of course this is a test data only
for k = 1:numel(index1)
  i = indexI(k);
  j = indexJ(k);
  ...
end

MATLAB: Vectorize a simple code

Note: See https://www.mathworks.com/matlabcentral/answers/35676-why-not-use-square-brackets : Even omitting the unneeded square brackets will accelerate the copde already.

A = rand(56);  % If I understand your inputs correctly:
B = rand(56);
tic;
for k = 1:100
  C = zeros(size(A));
  for j=[1:size(C,1)]
    for k=1:size(C,2)
      C(j,k)=sum(sum(A([1:j],[1:k]).*B([j:-1:1],[k:-1:1])));
    end
  end
end
toc
tic;
for k = 1:100
  C = zeros(size(A));
  for j=1:size(C,1)
    for k=1:size(C,2)
      C(j,k)=sum(sum(A(1:j,1:k).*B(j:-1:1,k:-1:1)));
    end
  end
end
tic
tic;
for k = 1:100
  C = zeros(size(A));
  for k = 1:size(C,2)
    BB = B(end:-1:1, k:-1:1);
    for j = 1:size(C,1)
      C(j, k) = sum(sum(A(1:j, 1:k) .* BB(end-j+1:end, :)));
    end
  end
end
toc
Elapsed time is 5.530599 seconds.
Elapsed time is 4.280142 seconds.
Elapsed time is 3.919369 seconds.

I assume conv2 is a much better approach, although I cannot include the reverted parts of B yet.

But it is worth to know this detail in general: avoid unneeded square brackets. You see a corresponding MLint warning in the editor also: the small orange mark under the [.

Best Answer

Related Solutions

MATLAB: For loop with multiple variables

MATLAB: Vectorize a simple code

Related Question