MATLAB: Replacing all numbers in a certain row

change valuesinputloop

Hi Guys Is there a way to replace all values in a row if just one value in the row meet a condition. Given a random 5×5 matrix. my condition is, if one number in a row is equal to -3, then all values in that row must be changed to -3.

To start with I thought that i could make a for loop, and then check each row and see if it meet the condition

Thank you in advance!

-David

Best Answer

Where M is your matrix:

M(any(M==-3,2),:) = -3

For example:

>> M = randi(9,5);
>> M(4,2) = -3
M =
   5   2   5   1   7
   2   3   5   8   3
   6   3   4   9   5
   8  -3   9   7   2
   5   6   8   8   9
>> M(any(M==-3,2),:) = -3
M =
   5   2   5   1   7
   2   3   5   8   3
   6   3   4   9   5
  -3  -3  -3  -3  -3
   5   6   8   8   9

Related Solutions

MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

Start with "If an entry in B is greater than or equal to zero": You can either run a loop over all elements of B or use "logical indexing":

% Linear indexing:
for k = 1:numel(B)
   if B(k) >= 0
     ...
   end
end

Or two indices for rows and columns:

for r = 1:size(B, 2)
  for c = 1:size(B, 1)
    if B(r, c) >= 0
       ...
    end
  end
end

Or "logical indexing":

index = (B >= 0);
disp(B(index))

Now try to use this to modify B. Use the mentioned terms to search in the documentation and in the internet.

MATLAB: Matrix repetition

   out = repmat(M,1,k);

Best Answer

Related Solutions

MATLAB: How to modify a matrix to change the entries >=0 and multiply it by 5 AND to change the entries <0 and add 2 to those entries

MATLAB: Matrix repetition

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