MATLAB: How to have the final vector

directionif statement

Hi all,
I've written the following script to calculate the wind direction from u and v components, taking into consideration the quadrants.
The problem is that I should have the final vector for the plot.
Where am I mistaken?
Note: U10 and V10 have a dimension of (1*120).
Thanks for the help.
for i = 1:length (U10);
  if(V10 > 0)   
      kk = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 180);
  elseif (U10 < 0 & V10 < 0) ;
      kk = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 0);
  elseif (U10 > 0 & V10 < 0);
      kk = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 360);
      end
end

Best Answer

Is the purpose of your loop to compare the values of V10 and U10 element-wise? If so, you would need to modify slightly: 
if V10(i) > 0  %compares the i'th element of V10 to 0
Secondly is kk the vector you're trying to create? If so, you'd need to make a similar adjustment (also, with a small vector it doesn't matter so much, but for larger ones, you'll speed things up if you pre-populate kk). Example: 
        kk = nan(size(U10)); %creates empty vector for kk
        for i = 1:length (U10); 
            if(V10(i) > 0) %compares the i'th element of V10 to 0  
                kk(i) = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 180);
            elseif (U10(i) < 0 & V10(i) < 0) ;
                kk(i) = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 0);
            elseif (U10(i) > 0 & V10(i) < 0);
                kk(i) = ((180 / pi) * atan(U10(:,i)/V10(:,i)) + 360);
            end
        end
Sorry if I misunderstan your question...
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