MATLAB: Compute trig. function in symbolic matrix

functionsMATLABmatrixsymbolictrig

Hi,

I have a symbolic matrix (as shown below). I would like for matlab to compute the trig functions with non-th5 values. How do I go about this.

Thanks in advance.

[         cos(th5),        -sin(th5),        0, 0]
[ cos(90)*sin(th5), cos(90)*cos(th5), -sin(90), 0]
[ sin(90)*sin(th5), sin(90)*cos(th5),  cos(90), 0]
[                0,                0,        0, 1]

Best Answer

Are you referring to reducing the sin(90) and cos(90) to the corresponding constant values? Because if you are then you need to take into account that sin() and cos() operate in radians, not in degrees. But this is your purpose then vpa() the symbolic matrix.

If you are wanting to substitute a numeric value for th5 then use subs(), possibly in conjunction with vpa() or double()

 subs(TheMatrix, th5, 1.238343)      %put in a particular numeric value

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MATLAB: Multiplication of matrices with Multiple variables

Not sure how you are getting the 'same value'. Your code as it is will not run in the first place.

Try this:

%case I
th1 = 0;
th2 = 0;
th3 = 0;
th4 = 0;
th5 = 0;
th6 = 0;
display('Case 1');
T1 = [cos(th1) 0 -sin(th1) 0; sin(th1) 0 -cos(th1) 0; 0 -1 0 0; 0 0 0 1];
T2 = [cos(th2) -sin(th2) 0 (260*cos(th2)); sin(th2) cos(th2) 0 (260*sin(th2)) ; 0 0 1 0; 0 0 0 1];
T3 = [cos(th3) 0 sin(th3) (-30*cos(th3)); sin(th3) 0 -cos(th3) (-30*sin(th3)) ; 0 1 0 0; 0 0 0 1];
T4 = [cos(th4) 0 sin(th4) 0; sin(th4) 0 -cos(th4) 0; 0 1 0 270; 0 0 0 1];
T5 = [cos(th5) 0 sin(th5) 0; sin(th5) 0 -cos(th5) 0; 0 1 0 0; 0 0 0 1];
T6 = [cos(th6) -sin(th6) 0 0; sin(th6) cos(th6) 0 0; 0 0 1 90; 0 0 0 1];
T = T1 * T2 * T3 * T4 * T5 * T6;
display(T);
%case II
th1 = pi/2;
th2 = 0;
th3 = pi;
th4 = 0;
th5 = 0;
th6 = 0;
display('Case 2');
T1 = [cos(th1) 0 -sin(th1) 0; sin(th1) 0 -cos(th1) 0; 0 -1 0 0; 0 0 0 1];
T2 = [cos(th2) -sin(th2) 0 (260*cos(th2)); sin(th2) cos(th2) 0 (260*sin(th2)) ; 0 0 1 0; 0 0 0 1];
T3 = [cos(th3) 0 sin(th3) (-30*cos(th3)); sin(th3) 0 -cos(th3) (-30*sin(th3)) ; 0 1 0 0; 0 0 0 1];
T4 = [cos(th4) 0 sin(th4) 0; sin(th4) 0 -cos(th4) 0; 0 1 0 270; 0 0 0 1];
T5 = [cos(th5) 0 sin(th5) 0; sin(th5) 0 -cos(th5) 0; 0 1 0 0; 0 0 0 1];
T6 = [cos(th6) -sin(th6) 0 0; sin(th6) cos(th6) 0 0; 0 0 1 90; 0 0 0 1];
T = T1 * T2 * T3 * T4 * T5 * T6;
display(T);

Works fine. If you want an optimized code and dont want to repeat the T1 to T6 equations, you can write them in a function and just call the function multiple times.

MATLAB: Plot function of 3 variables

Three variables plus one result = 4 dimensions. To represent the 4th dimension you will need to use color or transparency or shading or marker size or marker shape.

Best Answer

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