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Re: extracting values from an array [message #44280 is a reply to message #44279]

Wed, 01 June 2005 11:58

R.G. Stockwell
Messages: 363
Registered: July 1999

Senior Member

"Francois L." <fleduc@lycos.com> wrote in message
news:1117651509.818205@news.drenet.dnd.ca...
> Hello,
>
> Probably a simple question...
>
> I have an array A and I want to extract values greater than -1.
>> A = [2,-1, -1, 3,-1,-1, 4, -1]
>> w = where(a gt -1)
>> if w[0] gt -1 then b = a[w]
>
> Is there a cleaner and faster way to do this ?
>
> Thanks,
>
> Fran�ois.

Hi,

cleaner? I doubt it, I think where() is pretty clean :) and I don't think
writing
two lines of code is being excessively verbose.

faster? you could try a histogram call, with the reverse indices keyword,
since histogram is a magic routine that, when used non-intuitively,
usually leads to superior results. Use 2 bins, -1000 to -1, and 0 to 1000
for
instance, where 1000 is chosen to be larger than any of your data.
This may be less clean than the where() call.

If, however, you are looping through a large number of A vectors,
perhaps you could do a histogram call on all of them (or something like
that).
Or if you are looping over different criteria (gt -1, then gt 1, etc) that
could
be accomplished in one histogram call.

Exactly how big is this A array that you are not satisfied with the speed of
where?

Cheers,
bob

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[Message index]

		Re: extracting values from an array By: Kenneth P. Bowman on Thu, 02 June 2005 17:32
		Re: extracting values from an array By: caitouer on Thu, 02 June 2005 14:01
		Re: extracting values from an array By: Michael Wallace on Wed, 01 June 2005 13:14
		Re: extracting values from an array By: Benjamin Hornberger on Wed, 01 June 2005 13:06
		Re: extracting values from an array By: Michael Wallace on Wed, 01 June 2005 12:49
		Re: extracting values from an array By: Francois L. on Wed, 01 June 2005 12:19
		Re: extracting values from an array By: R.G. Stockwell on Wed, 01 June 2005 11:58

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