[SciPy-User] SciPy-User Digest, Vol 91, Issue 21
Wed Mar 16 04:26:27 CDT 2011
> Message: 6
> Date: Tue, 15 Mar 2011 14:23:47 -0500
> From: Warren Weckesser <email@example.com>
> Subject: Re: [SciPy-User] 1 dimensional interpolation of vectors
> To: SciPy Users List <firstname.lastname@example.org>
> Content-Type: text/plain; charset="utf-8"
> On Tue, Mar 15, 2011 at 1:33 PM, Michael Hull <email@example.com>wrote:
>> Sorry for the confusing title!
>> Firstly, thanks for all the great work on numpy and scipy, its very
>> What I have is an array of time recordings of various properties. If
>> have recordings of prop1,prop2,prop3,prop4.... propN, and for each
>> recording, I have the values at millisecond time intervals, stored in
>> a 2 dimensional array.
>> The properties are not linked, what I am trying to do is to find the
>> value at say t=2.4ms, i.e. a non integer millisecond, by linearly
>> interpolating between the two time points 2ms and 3ms.
>> I can do this in one dimension using scipy.interpolate.interp1d for
>> each property, but what I would like to do is get an entire row in one
>> go,, because the number of properties is
>> pretty large.
>> I can write this myself, but I was wondering if there was already
>> something built in?
> interp1d can take a 2D array for the y value. For example,
> In : x = array([0.0, 1.0, 2.0, 3.0])
> In : y = array([[1.0, 0.0, 0.5, 10.5],[-4, 2, 2, 0]])
> In : func = interp1d(x, y)
> In : func(0.5)
> Out: array([ 0.5, -1. ])
> In : func(1.1)
> Out: array([ 0.05, 2. ])
> In : func(2.75)
> Out: array([ 8. , 0.5])
> So if you have a 2D array of measurements--one row for each "prop"--you can
> use interp1d without a loop. If each property is a column, you can use the
> 'axis=0' keyword argument in interp1d, or transpose the array.
Ah, thats great, I'll give this a try.
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