Compare two columns in a matrix, perform if statement.

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Jeremy 2014-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/133381-compare-two-columns-in-a-matrix-perform-if-statement

评论： Jeremy 2014-6-9

I have a matrix (A) comprised of two columns each containing values which range from above and below zero. I want to perform different operations for the columns depending on which is above or below zero, and then put the answer in a third column. But currently, the code I am writing does not work. Any help much appreciated.

Example data: -0.758061618089340 -0.268100439060114 0 -0.721712386617467 -0.255203506765691 0 -2.45015138605334 5.44561062848519 0

Code tried: if (A(:,1)>0) && (A(:,2))<0) A(:,3) = (atan(A(:,1)/A(:,2))/(pi*180))+180;

Produces the following error: Operands to the and && operators must be convertible to logical scalar values.

Thanks for any help.

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Answer 1

David Sanchez 2014-6-9

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Your sample data is not very useful, but I think you are trying to do something like this:

%sample data
 A=[-0.758061618089340 -0.268100439060114;
     0 -0.721712386617467;
     -0.255203506765691 0;
     5.44561062848519 -1];
   N_col = size(A,1);
   A=[A, zeros(N_col,1)];
  for k=1:N_col
      if (A(k,1)>0) && (A(k,2)<0) 
          A(k,3) = (atan(A(k,1)/A(k,2))/(pi*180))+180;
      end
  end