symbolic pkg functions for sym2poly

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symbolic pkg functions for sym2poly

Doug Stewart-4
I am trying to make a demo of using the symbolic pkg to solve 
2 simultaneous Laplace equations, and the use the results with a function_handle.

syms f1 f2 x y1 y2 s k1 k2 c m1 m2
f1 =  m1*s^2 * y1 == s*(c*(y2-y1))+k1*(y2-y1)
f2 =m2*s^2 * y2 == s*(c*(y1-y2)) + k1*(y1-y2)+k2*(x-y2)
[y1a, y2a]=solve(f1,f2,y1,y2)

This code works and gives

y1a = (sym)

                     -k₂⋅x⋅(c⋅s + k₁)
            2       ⎛                      2⎞ ⎛                              2⎞
  (c⋅s + k₁)  - ⎝c⋅s + k₁ + m₁⋅s ⎠⋅⎝c⋅s + k₁ + k₂ + m₂⋅s ⎠

Now I want it to be shown in power of s

I have found a poly2sym  but I need a sym2poly

I also tried expand and it does show s^4 etc, but I can't get it to contract back to powers of s

Colin do you know how to do this?