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Hi Jouni,
Jouni K Sepp=E4nen wrote:
>On 2004年11月14日 18:08:59 +0200, Jouni K Sepp=E4nen
><jou...@gm...> wrote:
> =20
>
>>Here's what I'm using to emulate Matlab's find; it only seems to work
>>with Numeric, not numarray
>> =20
>>
>
>Oops - actually it seems that after
>
>from matplotlib.numerix import ravel, indices, compress
>
>the function works whether numerix is using numarray or Numeric.
>
>Making a special case of single-dimensional inputs is not very
>elegant, but doing otherwise would break compatibility with the
>existing mlab.find; and I guess there is no way in Python of emulating
>Matlab's detection of the number of output arguments.
> =20
>
I looked at this a while back, and came to the same conclusion. Thats an=20
interesting question, can Python determine the number of output=20
arguments? I dont know of a convenient function call, but it seems like=20
that information must exist somewhere. I'll ask at c.l.p.
Darren

On 2004年11月14日 18:08:59 +0200, Jouni K Sepp=E4nen
<jou...@gm...> wrote:
>
> Here's what I'm using to emulate Matlab's find; it only seems to work
> with Numeric, not numarray
Oops - actually it seems that after
from matplotlib.numerix import ravel, indices, compress
the function works whether numerix is using numarray or Numeric.
Making a special case of single-dimensional inputs is not very
elegant, but doing otherwise would break compatibility with the
existing mlab.find; and I guess there is no way in Python of emulating
Matlab's detection of the number of output arguments.
--=20
Jouni K Sepp=E4nen
http://www.iki.fi/jks

Hi,
In Matlab, the command
 [i,j] =3D find(mat >=3D 3)
causes i and j to hold the indices where the condition holds. (If
there is only one output argument, it will hold indices to the
flattened version of the condition.) Matplotlib's mlab.find() seems to
work for one-dimensional arrays only.
Here's what I'm using to emulate Matlab's find; it only seems to work
with Numeric, not numarray, and I have no idea whether this is an
efficient way to achieve the goal. I was going to suggest that the
utility be included in matplotlib, but perhaps it should then be
generalized to work with numarray as well. I wonder if anyone has any
ideas on how to do this? I'm a newcomer to matplotlib (and Numeric,
etc.), so please do point out if there is a simpler way to achieve the
effect of Matlab's find.
def find(condition):
 """
 Return the indices where condition is true.
 For arrays of N>=3D2 dimensions, returns a tuple T of N arrays
 such that the condition is true at indices (T[0][i],...,T[N-1][i]).
 """
 sh =3D condition.shape
 if len(sh) =3D=3D 1:
 return nonzero(condition)
 idx =3D indices(sh)
 cond =3D ravel(condition)
 return tuple([compress(cond, ravel(idx[i]))=20
 for i in range(len(sh))])
--=20
Jouni K Sepp=E4nen
http://www.iki.fi/jks