MATLAB: How to select true values

indextrue

I have 2 matrices and 4 conditions for it

like positive positive negative positive positive negative abd negative negative

i have converted them into indices matrix

and now it should go further when the answer is true

if true
  % code
A=[-1,2,3,4,-5]
 B= [-6,-7,8,9,10]
   i1=A<0;i2=A>0;i3=B<0;i4=B>0;

for example in i1 and i3 how can select 1 and 1 on the same index

here -1 and -6 and the go further

Best Answer

>> A=[-1,2,3,4,-5]
 B= [-6,-7,8,9,10]
   i1=A<0;
   i2=A>0;
   i3=B<0;
   i4=B>0;
         AA= A(i1 & i3)
          BB=B(i2 & i4)
A =
      -1     2     3     4    -5
B =
      -6    -7     8     9    10
AA =
      -1
BB =
       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: Sum of vector by group

a=[1 4 1 -3 -6 9 9 1 1 1 -1 -1 -4];
idx = cumsum([0 abs(diff(sign(a)))==2])+1;
res = accumarray(idx.',a.')

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: Sum of vector by group

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