Arrange linear equation w.r.t variables

Hello,

How I can arrange the following linear equations such that it results same equations but with sequence of a,b,c and d?

R =

[0.8978*c - 0.8047*b - 0.020299*a, 0.8978*d - 0.094800*b - 0.106799*a]

[ 0.091199*a + 0.13200*c - 0.8047*d, 0.091199*b - 0.106799*c + 0.0575*d]

Thanks.

[Azzi Abdelmalek]

What does that mean?

[SMK]

It means that how I can arrange any result w.r.t its variables, so that I can get coefficient matrix in sequence of variables. Might be this time I could explain it.

Answer 1

[Thorsten]

The columns are a, b, c, d and the values in row 1, 2, 3 are the coefficients in your equation 1, 2, 3. Use zero if there is no coefficient, such as for d in your first equation

 >> R = [-0.020299  -0.8047 0.8978 0 ; -0.106799 -0.094800 0 0.8978; 0.091199 0 0.13200 -0.8047; 0 0.091199 -0.106799 0.0575]

 R =

   -0.0203   -0.8047    0.8978         0
   -0.1068   -0.0948         0    0.8978
    0.0912         0    0.1320   -0.8047
         0    0.0912   -0.1068    0.0575

You can then compute a solution to R*[a;b;c;d] = [1;5;30;4] (for example) by

 R\[1;5;30;4];

[SMK]

Thanks, but how we reached on this arranged coefficient matrix?

[Thorsten]

Convert each equation of the sort c1*a + c2*b + c3*c + c4*d to a row of your matrix

c1 c2 c3 c4

So for example 0.8978*c - 0.8047*b - 0.020299*a gives values c4 = 0 (because there is no d), c3 = 0.8978 (the coefficient in front of c), c2 = -0.8047 (the coefficient in front of b) and finally c1 = -0.02099 (the coefficient in front of a):

 -0.0203   -0.8047    0.8978         0

Same for the other terms you have.