From symbolic to numeric in matlab

Question

In my problem, there are some matrices like

T_x=[ cos(q1) sin(q1+q2) cos(q1) -sin(q2);
      0       0           1      -1;
      sin(q4) 0           1      q1;
      0       0           0      1]

Moreover I have the q values such as: q=[0.2 0.05 -2 -3.5]

How can I insert the q values into T_x matrix?

Thanks

Answer 1

One way would be to have a matrix-returning function that takes the values as an argument:

>> T_x = @(q) [ cos(q(1)) sin(q(1)+q(2)) cos(q(1)) -sin(q(2));
                0          0             1         -1;
                sin(q(4))  0             1         q(1);
                0          0             0         1];

>> T_x([.2 .05 -2 -3.5])

ans =

    0.9801    0.2474    0.9801   -0.0500
         0         0    1.0000   -1.0000
    0.3508         0    1.0000    0.2000
         0         0         0    1.0000

This has the benefit of not needing the symbolic package - it's portable to Octave.