How to insert variables (string) in MATLAB function

function R=rotmatx(axis,q)
if axis=='x'    
    R=[1 0 0;0 cos(q) -sin(q); 0 sin(q) cos(q)];
elseif axis=='y'
    R=[cos(q) 0 sin(q); 0 1 0; -sin(q) 0 cos(q)];
elseif axis=='z'
    R=[cos(q) -sin(q) 0;-sin(q) cos(q) 0; 0 0 1];
else
    fprintf('invalid axis');
end 

so, i want the output when i call this function

rotmatx('x','t')

the output should be

[1, 0, 0]

[0, cos(t), -sin(t)]

[0, sin(t), cos(t)]

but there is error.

Can someone please help me out for this.

Thank You.

Answer 1

[Walter Roberson]

rotmatx('y', 'p')

ans = 

rotmatx('z', pi/6)

ans = 

function R=rotmatx(axis,q)
    Q = sym(q);
    if axis=='x'    
        R=[1 0 0;0 cos(Q) -sin(Q); 0 sin(Q) cos(Q)];
    elseif axis=='y'
        R=[cos(Q) 0 sin(Q); 0 1 0; -sin(Q) 0 cos(Q)];
    elseif axis=='z'
        R=[cos(Q) -sin(Q) 0;-sin(Q) cos(Q) 0; 0 0 1];
    else
        fprintf('invalid axis');
    end 
end

[Pk Verma]

Thank you sir.

Answer 2

[KSSV]

syms t
R=[1 0 0;0 cos(t) -sin(t); 0 sin(t) cos(t)]

R = 

[Pk Verma]

I want to write the R matrix with the help of function. I dont want to write each R matrix for different angle.

[KSSV]

You can follow the above method and write into a function.

[Pk Verma]

Do you mean this

function R=tst(t)
syms t
R=[1 0 0;0 cos(t) -sin(t); 0 sin(t) cos(t)];
end 

now

tst('p')

now output is...

[1, 0, 0]

[0, cos(t), -sin(t)]

[0, sin(t), cos(t)]

but output should be

[1, 0, 0]

[0, cos(p), -sin(p)]

[0, sin(p), cos(p)]

if i done anything wrong then please write function and then function calling code.