Remove masked elements from an array

[John Machin]

30/04/2002 10:27:40 AM, holger krekel <pyth at devel.trillke.net> wrote:

>On Mon, Apr 29, 2002 at 05:09:57PM -0700, John Machin wrote:
>> holger krekel <pyth at devel.trillke.net> wrote in message news:<mailman.1020102370.5619.python-list at python.org>...
>> > On Mon, Apr 29, 2002 at 01:26:25PM -0400, PoulsenL at capecon.com wrote:
>> > > I have a Numeric array with missing elements from which I wish to calculate
>> > > a histogram.  However, in order to do so I must first remove the 'None'
>> > > values from the array.  I have a kludgy solution, but I was wondering if
>> > > someone could point me in the right direction on what is the proper method
>> > > of collapsing a masked array to just the non-masked values.
>> > 
>> > there are too solutions. choose yourself :-)
>> > 
>> > nums = [ 1,2,3,None,2,3]
>> > 
>> > #version1
>> > def f(x): return x is not None
>> > newnums = filter(f, nums)
>> > 
>> > #version2
>> > newnums = [ x for x in nums if x is not None]
>> > 
>> > The first version uses filter. 
>> > 'filter' calls 'f' for every item in 'nums' and puts
>> > the result into the new list iff it has a 'true' value.
>> > 
>> > The second version uses list comprehension.
>> > It basically does the same if you look closely
>> > at it. 
>> 
>> *Don't* try this if zero is a valid value for your histogram:
>
>i think you are on the wrong track.

Re-read my posting, especially the bit that you left out.
What you posted is correct as far as it goes.
I was pointing out to the OP that he shouldn't try

newnums = f(None, nums)
[this is the line that you mentally and physically snipped]

Grammar:
'Don't try this' <blah blah> <colon>
   <referent of 'this'>

HTH,
John