# [Numpy-discussion] Numpy Advanced Indexing Question

Jack.Cook@shel... Jack.Cook@shel...
Wed Jul 16 17:12:47 CDT 2008

```Robert,

I can understand how this works if K is a constant time value but in my case K varies at each location in the two-dimensional slice. In other words, if I was doing this in a for loop I would do something like this

for i in range(numI):
for j in range(numJ):
k = slice(i,j)
trace = cube(i,j,k-half_width:k+half_width)
# shove trace in sub volume

What am I missing?

- Jack

-----Original Message-----
From: numpy-discussion-bounces@scipy.org
[mailto:numpy-discussion-bounces@scipy.org]On Behalf Of Robert Kern
Sent: Wednesday, July 16, 2008 4:56 PM
To: Discussion of Numerical Python
Subject: Re: [Numpy-discussion] Numpy Advanced Indexing Question

On Wed, Jul 16, 2008 at 16:45,  <Jack.Cook@shell.com> wrote:
> Greetings,
>
> I have an I,J,K 3D volume of amplitude values at regularly sampled time
> intervals. I have an I,J 2D slice which contains a time (K) value at each I,
> J location. What I would like to do is extract a subvolume at a constant +/-
> K window around the slice. Is there an easy way to do this using advanced
> indexing or some other method? Thanks in advanced for your help.

cube[:,:,K-half_width:K+half_width]

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
-- Umberto Eco
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