Applying a function to a 2-D numarray

[Steven Bethard]

Matt Feinstein wrote:
> Is there an optimal way to apply a function to the elements of a two-d
> array?
> 
> What I'd like to do is define some function:
> 
> def plone(x):
>      return x+1
> 
> and then apply it elementwise to a 2-D numarray. I intend to treat the
> function as a variable, so ufuncs are probably not appropriate-- I
> realize that  what I'm looking for won't be terrifically efficient,
> but I'd like to avoid doing it in the -worst- possible way.
> 
> Some things I've looked at include things like
> 
> def applyfun(m,f):
>      elist = [f(e) for e in m]
>      return reshape(elist,m.shape)
> 
> however, I can see that this looks neat but probably generates several
> copies of the array, which is not so neat.
> 
> Is there a better way?

I must be missing something, because the simplest possible thing seems 
to work for me:

py> import numarray as na
py> def plus1(arr):
...     return arr + 1
...
py> def apply_func(arr, f):
...     return f(arr)
...
py> a = na.arange(20, shape=(4, 5))
py> a
array([[ 0,  1,  2,  3,  4],
        [ 5,  6,  7,  8,  9],
        [10, 11, 12, 13, 14],
        [15, 16, 17, 18, 19]])
py> apply_func(a, plus1)
array([[ 1,  2,  3,  4,  5],
        [ 6,  7,  8,  9, 10],
        [11, 12, 13, 14, 15],
        [16, 17, 18, 19, 20]])

Is this not what you wanted?

STeVe