[SciPy-User] convolve/deconvolve

[François Boulogne]

Hi,

I need to deconvolve a signal with a filter. I had a look in the
documentation. The function exists but the docstring is missing and I'm
not satisfied of the result I got from a "simple" example.

filter = np.array([0,1,1,1,1,0])
step = np.array([0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1])
# I convolve both
res = convolve(step, filter, 'valid')
# and it returns a slope as expected
array([0, 0, 1, 2, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4])

Now, I want to deconvolve.
deconvolve(res, filter)
# oops, it raises an exception
ValueError: BUG: filter coefficient a[0] == 0 not supported yet

# well, let's try this
deconvolve(res, filter+1e-9)
(array([  0.00000000e+00,   0.00000000e+00,   1.00000000e+09,
        -9.99999999e+17,   9.99999999e+26,  -9.99999999e+35,
         9.99999999e+44,  -9.99999999e+53,   9.99999999e+62,
        -9.99999999e+71,   9.99999999e+80,  -9.99999999e+89]),
 array([  0.00000000e+00,   0.00000000e+00,   1.11022302e-16,
        -8.27130862e-08,  -4.42500000e+01,   5.46901335e+10,
         8.27266814e+19,   7.56858250e+28,  -8.74285726e+37,
         9.99419626e+46,   8.27205507e+55,  -8.26933326e+64,
         9.99999999e+89,   9.99999999e+89,   9.99999999e+89,
         1.00000000e+90,   9.99999999e+80]))

It's better but I do not recognize my signal :)
1/ Am I misunderstanding or missing something?
2/ How can I do it correctly?

I also noted that no test exists for deconvolve() :(

Cheers,
François.