How to multiply two matrix in such a way that I can store individual values of the matrix

for x=20:1:75

[X]= [cos(x) sin(x); sin(x) cos(x) ]* [1; 2];

end

When I am using this code i can only use the last value which in this case comes out to be for x= 75. Is there an efficient way to code so that I can Matrix with all the values x ranging from 20 to 75.

Answer 1

[David Hill]

x=20:75;
X=[cosd(x).*sind(x); sind(x).*cosd(x)].*[1; 2];

[Kushagra Kirtiman]

But I dont want an array. I want to save the values in different variable

for example

for a=30:1:75

[T1]= [ (cos(a))^2 (sin(a))^2 -2*cos(a)*sin(a); (sin(a))^2 (cos(a))^2 2*cos(a)*sin(a); cos(a)*sin(a) -cos(a)*sin(a) (cos(a))^2-(sin(a))^2 ];

T1

end

here I have to store the matrix in different variables so that I can have values of T matrix for all values of a.

[Image Analyst]

You certainly don't want 46 different variables T1, T2, T3, through T46. That would be an absolutely horrible idea. Why? See the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2C_A10_in_a_loop.3F

[Kushagra Kirtiman]

I want this because I am calculating coordinate transformation matrices for different winding angles so in order to calculate the siffness matrix of the lamina for different winding angles. For eg for angles 20 to 75 I want individual stifness matrcies

[Torsten]

Then copy-paste.

[David Hill]

Better to do a 3-D matrix so you can index into it.

a=30:75;
T= reshape([(cosd(a)).^2; (sind(a)).^2; -2*cosd(a).*sind(a); (sind(a)).^2;...
    (cosd(a)).^2; 2*cosd(a).*sind(a); cosd(a).*sind(a);...
    -cosd(a).*sind(a); (cosd(a)).^2-(sind(a)).^2 ],3,3,[]);

[Stephen23]

"I want this because I am calculating coordinate transformation matrices for different winding angles so in order to calculate the siffness matrix of the lamina for different winding angles. For eg for angles 20 to 75 I want individual stifness matrcies "

Using lots of separate variables would be a very poor way to achieve that. Your proposed approach would require dynamically naming variables, which forces you into writing slow, complex, inefficient, obfuscated, code which is liable to bugs and harder to debug.

The neat, simple, and very efficient approach is to use very simple indexing, e.g. into a cell array:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

So far you have no given any reason why you cannot use simpler, easier, much more efficient indexing.