How do I extract each value from a column matrix and subsitute in a equation?

Hello MATLAB Community,

I have a small problem with regards to for loop.

I am trying to use the for loop to solve an equation and store all the values from that particular equation, but I am facing a problem where the loop is considering all values of a matrix to solve it.

for example : a1 = (-25 : 25); a2 = (-25 : 25); a3 = (-25 : 25);

Now I use the combvec function the find all possible combinations

comb = (combvec(a1,a2,a3)); and then I say

phi = comb(1,:);

theta = comb(2,:);

psi = comb(3,:);

Now, I need to subsitute each value of phi, theta and psi (all values of column 1 of comb matrix) into the equation:

ROT = [(cos(phi)*cos(psi))-(cos(theta)*sin(phi)*sin(psi)) -(cos(phi)*sin(psi))-(cos(theta)*cos(psi)*sin(phi)) (sin(phi)*sin(theta));...

(cos(psi)*sin(phi))+(cos(phi)*cos(theta)*sin(psi)) (cos(phi)*cos(theta)*cos(psi)-sin(phi)*sin(psi)) -(cos(phi)*sin(theta));...

(sin(theta)*sin(psi)) (cos(psi)*sin(theta)) cos(theta)];

Similarly, for the next iteration I will consider all values of column 2 of comb matrix and so on, upto the last column of the comb matrix.

Can anyone please help me with any suggestions.

Thank you in advance!!

I really appreciate your help.

Kind regards,

Shiv

Answer 1

[Matt J]

Change all of your '*' operators to elementwise operator '.*'

res=@(z) reshape(z,1,1,[]);

phi = res( comb(1,:) );
theta = res( comb(2,:) );
psi = res( comb(3,:)  );

ROT = [(cos(phi).*cos(psi))-(cos(theta).*sin(phi).*sin(psi)) -(cos(phi).*sin(psi))-(cos(theta).*cos(psi).*sin(phi)) (sin(phi).*sin(theta));...
(cos(psi).*sin(phi))+(cos(phi).*cos(theta).*sin(psi)) (cos(phi).*cos(theta).*cos(psi)-sin(phi).*sin(psi)) -(cos(phi).*sin(theta));...
(sin(theta).*sin(psi)) (cos(psi).*sin(theta)) cos(theta)];

[Shiv Karpoor]

Hi Matt,

I have tried it yesterday, it doesn't give me the answer in the way I want it by changing the operator to elementwise.

But any ways your updated answer worked, I just tried it.

This res=@(z) reshape(z,1,1,[]); made a difference. I am getting the output the way I want it in a 3x3 matrix.

Thank you so much, I really Appreciate it.

Kind Regards,

Shiv