MATLAB: Change the value in a matrix

changematrixvalue

I have any matrix I need a code such that if the absolute value of a value in the matrix less than 3, then this value equal to zero.

for example if i have the matrix:

    A=[-1,4,3;1,5,-7;3,-2,9]

the answer will be:

    B=[0,4,0;0,5,-7;0,0,9]

Thank you

Try

    >> B = A;
    >> B(abs(A)<=3) = 0
    B =
         0     4     0
         0     5    -7
         0     0     9

However, -7 isn't it "less than 3"?

A = [0 2 9; 5 7 3; 4 6 1];
C = [1 2 3; 4 5 6; 7 8 9];
B = zeros(6);
B(1:3,1:3) = A;
B(4:6,4:6) = C;

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.