sorry by the late reply... I still cannot take the time to answer this
question.... but I will do it soon
2013/11/25 Chris Smith <smi...@gmail.com>
> In the code you last posted, you do a substitution of new_var with vi and
> then differentiate wrt new_var. This will necessarily give you 0, won't it?
> Is this what you are trying to do:
>
> >>> def vdiff(x, vector):
> ... ans = []
> ... for vi in vector:
> ... if vi.is_Symbol:
> ... tmp = []
> ... for e in x:
> ... tmp.append(e.diff(vi))
> ... else:
> ... subs = {}
> ... new_var = Dummy()
> ... for s in vi.free_symbols:
> ... subs[s] = solve(new_var - vi, s)[0]
> ... tmp = []
> ... for e in x:
> ... e = e.subs(subs, simultaneous=True)
> ... d = Dummy('ei')
> ... e = idiff(d-e, d, new_var)
> ... e = e.subs({new_var: vi})
> ... tmp.append(e)
> ... ans.append(tmp)
> ... return ans
> ...
> >>> vdiff([x, x+y], [x, x-c])
> [[1, 1], [1, 1]]
> >>> vdiff([x, x+y], [x, exp(x)-c])
> [[1, 1], [exp(-x), exp(-x)]]
> >>> vdiff([x, x+y], [x, exp(x)-y])
> [[1, 1], [exp(-x), (-exp(x) + 1)*exp(-x)]]
>
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