my array subset method could be improved?

[Jim O'D]

Hi all

I have an array a=array([2,3,1]).

I want to extract an array with all the elements of a that are less than 0.

Method 1.
new = array([i for i in a if i < 0])

Method 2.
new = a[nonzero(a<0)]

I'm using Numeric arrays but can't seem to find a function that does this.

Am I missing a more obvious way to do it quickly?

Thanks

Jim

[Juho Schultz]

Re: my array subset method could be improved?

Jim O'D wrote:[color=blue]
> Hi all
>
> I have an array a=array([2,3,1]).
>
> I want to extract an array with all the elements of a that are less than 0.
>
> Method 1.
> new = array([i for i in a if i < 0])
>
> Method 2.
> new = a[nonzero(a<0)]
>
> I'm using Numeric arrays but can't seem to find a function that does this.
>
> Am I missing a more obvious way to do it quickly?
>
> Thanks
>
> Jim[/color]

new = Numeric.compres s(Numeric.less( a,0),a)

[Jim O'D]

Re: my array subset method could be improved?

[color=blue]
>
> new = Numeric.compres s(Numeric.less( a,0),a)[/color]

Ah, thank you!

Sorry about subject mangle, I gave a silly example first time round.

Jim

[Peter]

Re: my array subset method could be improved?

Jim O'D wrote:
[color=blue]
>Hi all
>
>I have an array a=array([2,3,1]).
>
>I want to extract an array with all the elements of a that are less than 0.
>
>Method 1.
>new = array([i for i in a if i < 0])
>
>Method 2.
>new = a[nonzero(a<0)]
>
>I'm using Numeric arrays but can't seem to find a function that does this.
>
>Am I missing a more obvious way to do it quickly?
>
>Thanks
>
>Jim
>
>[/color]
You could use filter (which is planned to be removed in Py3000). E.g.
"array(filter(l ambda x: x < 0, (-1, 2, -4, 5, 55, 9, -73, 5)))"

I tend to like "array(i for i in (-1, 2, -4, 5, 55, 9, -73, 5) if i <
0)" better though. (And its even shorter).

HTH,
Peter

[malik]

any good midi tutorials?

anybody know any good midi tutorials for python?
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