MATLAB: Value not multiplying by -1

if statementmultiplication

I have a nested if statement which works as it is supposed to until the last iteration.
Does anyone know why it is not multiplying the last value by -1?
w = x_0     % zero vector 
k = 0       % zero value
i=1         % initial value for count
j=-1        % coefficient
    for i = 1:n
      if Raw_Data(i,2) == Raw_Data (i,3)
          fprintf ('ERROR!!!!!)
      else if Raw_Data(i,3) == val            
              w(i,1) = Raw_Data(i,4)          
          else if Raw_Data(i,2) == val        
                  w(i,1) =  j* Raw_Data(i,4)   
                  % Rationalisation Not Working
              else  w(i,1)= j* Raw_Data(i,4)                        
              end
          end
      end
      i=i+1
  end

Best Answer

I would suggest to avoid the loop and use logical indexing:
ind = Raw_data(i,3) == val;
w(ind) = Raw_data(:,4);
w(~ind) = j*Raw_data(:,4);
if any(Raw_Data(i,2) == Raw_Data (i,3))
 error('values in column 2 and 3 are identical.')  
end
Note that in your code
else if Raw_Data(i,2) == val
is not needed, because
w(i,1) =  j* Raw_Data(i,4)
in any case.
And if w is a vector, w(i) is the same as w(1,i).
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