Re: [Pytables-users] Numpy Arrays to Structure Array or Table

[Anthony S. <sc...@gm...>]

Hi David,

I think that you can do what you want in one, rather long line:

hfile.createTable(grp, 'signal', description=np.array(zip(some_func(t, v)),
dtype=[('time', np.float64), ('value', np.float64)]))

Or two nicer lines:

arr = np.array(zip(some_func(t, v)), dtype=[('time', np.float64), ('value',
np.float64)])
hfile.createTable(grp, 'signal', description=arr)

zip() is your friend =).  If zip is too slow and you don't want to make
more than one copy, you could try something like this:

temparr = np.array(some_func(t, v)).T
arr = np.view(temparr, dtype=[('time', np.float64), ('value', np.float64)])

This really only works because both columns have the same dtype.

Of course, you can always keep basically what you have and loop through the
column names programmaticly:

for name, col in zip(A.dtype.names, some_func(t, v)):
    A[name] = col

I hope this helps!

Be Well
Anthony

On Wed, Aug 7, 2013 at 5:58 PM, David Reed <dav...@gm...> wrote:

> Hi there,
>
> I have some generic functions that take time series data with 2 numpy
> array arguments, time and value, and return 2 numpy arrays of time and
> value.
>
> I would like to place these arrays into a Numpy structured array or
> directly into a new pytables table with fields, time and value.
>
> Now Ive found I could do this:
>
>     t, v = some_func(t, v)
>
>     A = np.empty(len(t), dtype=[('time', np.float64), ('value',
> np.float64)])
>
>     A['time'] = t
>     A['value'] = v
>
>     hfile.createTable(grp, 'signal', description=A)
>     hfile.flush()
>
> But this seems rather clunky and inefficient.  Any suggestions to make
> this repackaging a little smoother?
>
>
>
>
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