MATLAB: Manipulating a sub-matrix

submatirx

I have the following way of subarray manipulation. I have an array called arr of dimension rxc, i loop goes from 1 to r-n, j loop goes from 1 to c-n, and I use as:

x=somefn(arr(i:i+n-1,j:j+n-1)(:),a);

I am getting error stating: cannot call or index to a temporary array at the :, please suggest remedy.

Best Answer

You can't chain indexing operations, so you can either create a temporary variable

subarr = arr(i:i+n-1, j:j+n-1);
x = somefn(subarr(:), a);

Or, since the colon here just does a reshape, call reshape explicitly:

x = somefn(reshape(arr(i:i+n-1, j:j+n-1), [], 1), a);

Related Solutions

MATLAB: What does for j = [1:i-1, i+1:n] mean

for j = [1:i-1, i+1:n]
  ...
end

is the same as:

for j = 1:n
  if j ~= i
     ...
  end
end

It runs a loop over all numbers from 1 to n, but excludes i . The loop index is the concatenation of the vectors 1:i-1 and i+1:n .

You can simply try it:

n = 10;
i = 7;
for j = [1:i-1, i+1:n]
  disp(j)
end

MATLAB: Fix the function hlp

By the way, this can be done in one line:

arr = reshape(1:n^2, n, n).' .^ ((1:n) .^ rem(0:n-1, 2))

Have fun with analyzing, how this works.

Is there a shorter solution?

Best Answer

Related Solutions

MATLAB: What does for j = [1:i-1, i+1:n] mean

MATLAB: Fix the function hlp

Related Question