Applying a For Loop to a matrix

Hi, I am very new to Matlab. I am struggling writing a For Loop to apply certain equations to each cell in a matrix. E.g. I have written the code; for i=1:100 PhaseAngle=atand((AngularVelocity(i,1))/K2(i+1,1)); end

in which AngularVelocity is a matrix of 1 column and 100 rows, K2 is a matrix of 1 column and 101 rows (which is why it is i+1 so it ignores the first column)

I want to to apply atand(angularvelocity/K2) for each row, however the PhaseAngle answer is overwritten every time for each cell. I need the answers in the same form as a 1 column 100 row matrix.

Also how would I do the same for a rolling summation equation;

xsumcos1=0; ysumsin1=0;

 for j=1:100
     xsumcos1=xsumcos1+cos(CouplingAngle1(j,1));
     ysumsin1=ysumsin1+sin(CouplingAngle1(j,1));
 end

Thank you in advance!

Answer 1

[Mischa Kim]

Alex, use

 for ii = 1:100 
    PhaseAngle(ii) = atand(AngularVelocity(ii)/K2(ii+1)); 
 end

I recommend using ii as the loop index rather than i, which is the imaginary unit in MATLAB. You can use the same approach for the other loop. Also, for large arrays you might want to pre-allocate memory before executing the loop:

 PhaseAngle = zeros(size(AngularVelocity));

[alex]

Hey, thanks that worked for the first equation but for the second I got the error message 'In an assignment A(I) = B, the number of elements in B and I must be the same.'

[Mischa Kim]

For the second loop you need to access the corresponding vector elements, something like:

 xsumcos1(1) = 0; 
 ysumsin1(1) = 0;
 for jj = 1:100   % same thing here, j is also used as the imag. unit
     xsumcos1(jj+1) = xsumcos1(jj) + cos(CouplingAngle1(jj));
     ysumsin1(jj+1) = ysumsin1(jj) + sin(CouplingAngle1(jj));
 end

[alex]

Yes! that works great. I have made an error in my calculations though.

I have 3 matrices of Coupling angles (CA1,CA2,CA3) all 100x1.

I want to get the sum of cos(CA1)+cos(CA2)+cos(CA3) and the sum of sin(CA1)+sin(CA2)+sin(CA3) How would I do that? Would I put all the Coupling Angle Matrices together to one matrix? and write code something like;

A=(CA1,CA2,CA3) % making the matrix

for jj=3:100

   xsumcos(jj)=cos(CA1)+cos(CA2)+cos(CA3)
   ysumsin(jj)=sin(CA1)+sin(CA2)+sin(CA3)
end

Thank you again!

[Mischa Kim]

In this case you can simply do:

 A       = [CA1 CA2 CA3];
 xsumcos = sum(cos(A),2);
 ysumsin = sum(sin(A),2);

[alex]

Thank you very much for your help!