iterator over a numarray?

[Alex Hunsley]

I'm looking for a way to iterate over all the items in a numarray.
Writing a few nested loops isn't going to cut it, because the numarray
in question could be of any dimension...
I am aware of the revel function, but that appears to just flatten the
numarray. What I need is an iterator that can give each value and the
coordinates in the array of that item....

thanks
alex

[Fernando Perez]

Alex Hunsley wrote:

I'm looking for a way to iterate over all the items in a numarray.
Writing a few nested loops isn't going to cut it, because the numarray
in question could be of any dimension...
I am aware of the revel function, but that appears to just flatten the
numarray. What I need is an iterator that can give each value and the
coordinates in the array of that item....

I'd suggest you repost this (and you other numarray question) directly to the
numarray list (numpy-dicsussion). The response rate tends to be better for
numpy/numarray specific questions on that list, since the users of those libs
don't always follow c.l.py regularly (though most follow it on and off).

Best,

f

[Colin J. Williams]

Alex Hunsley wrote:

I'm looking for a way to iterate over all the items in a numarray.
Writing a few nested loops isn't going to cut it, because the numarray
in question could be of any dimension...
I am aware of the revel function, but that appears to just flatten the
numarray. What I need is an iterator that can give each value and the
coordinates in the array of that item....

thanks
alex

Alex,

You might try something like:
import numarray as _num
a= _num.arange(48, shape= (4, 4, 3))
b= iter()
c= b.next()
print `c`
d= b.next()
print `d`
This gives:
array([[ 0, 1, 2],
[ 3, 4, 5],
[ 6, 7, 8],
[ 9, 10, 11]])
array([[12, 13, 14],
[15, 16, 17],
[18, 19, 20],
[21, 22, 23]])
You can see that we move along the first dimension.

ravel() flattens an array in situ, flat delivers a flattened array.

Colin W.

[Alex Hunsley]

Colin J. Williams wrote:

Alex Hunsley wrote:

I'm looking for a way to iterate over all the items in a numarray.
Writing a few nested loops isn't going to cut it, because the numarray
in question could be of any dimension...
I am aware of the revel function, but that appears to just flatten the
numarray. What I need is an iterator that can give each value and the
coordinates in the array of that item....

thanks
alex

Alex,

You might try something like:
import numarray as _num
a= _num.arange(48, shape= (4, 4, 3))
b= iter()
c= b.next()
print `c`
d= b.next()
print `d`
This gives:
array([[ 0, 1, 2],
[ 3, 4, 5],
[ 6, 7, 8],
[ 9, 10, 11]])
array([[12, 13, 14],
[15, 16, 17],
[18, 19, 20],
[21, 22, 23]])
You can see that we move along the first dimension.

ravel() flattens an array in situ, flat delivers a flattened array.

Colin W.

Hi Colin and Fernado
thanks for your replies!
After a little hunting I found something that did the trick via google
groups.
The article in question is here:

http://makeashorterlink.com/?P69D22AB8

it details a way to generate a list of coordinate and value pairs, e.g.
values from a 2d numarray would then be represented as:

(((0,0), 2), ((1,0), 65), ((2,0), 33), ....etc)

thanks!
alex