MATLAB: Problem using if with two vectors

for example if I have :

>> A=[1 -2 -8 4 19 -6 7 -18 9];

>> B=[-16 1 2 -4 -19 6 -17 18 -9];

and I'd like to create a new vector C which is equal to A if A<0 otherwise it should return B instead, like this:

C=[-16 -2 -8 -4 -19 -6 -17 -18 -9]

Best Answer

C=B
idx=A<0
C(idx)=A(idx)

Related Solutions

MATLAB: Consecutive combination of numbers from a list

>> (1:19)'+(0:2) % (1:m-n+1)'+(0:n-1)
ans =
     1     2     3
     2     3     4
     3     4     5
     4     5     6
     5     6     7
     6     7     8
     7     8     9
     8     9    10
     9    10    11
    10    11    12
    11    12    13
    12    13    14
    13    14    15
    14    15    16
    15    16    17
    16    17    18
    17    18    19
    18    19    20
    19    20    21

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.

Best Answer

Related Solutions

MATLAB: Consecutive combination of numbers from a list

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

Related Question