Hi everyone, I have two questions: 1. When I do v = u[:, :], it seems u and v still point to the same memory. e.g. When I do v[1,1]=0, u[1,1] will be zero out as well. What's the right way to duplicate an array? Now I have to do v = dot(u, identity(N)), which is kind of silly.
2. Is there a way to do Matlab style slicing? e.g. if I have i = array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y = x(i) would give me [1.1, 3.3] Now I'm using map, but it gets a little annoying when there are two dimensions. Any ideas?
Thanks!!!
-Y
On Thu, 20 Jan 2005 20:29:26 -0500 Yun Mao yunmao@gmail.com wrote:
Hi everyone, I have two questions:
- When I do v = u[:, :], it seems u and v still point to the same
memory. e.g. When I do v[1,1]=0, u[1,1] will be zero out as well. What's the right way to duplicate an array? Now I have to do v = dot(u, identity(N)), which is kind of silly.
v = na.array(u)
- Is there a way to do Matlab style slicing? e.g. if I have
i = array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y = x(i) would give me [1.1, 3.3] Now I'm using map, but it gets a little annoying when there are two dimensions. Any ideas?
have a look at the "take" method.
Simon.
Simon Burton wrote:
On Thu, 20 Jan 2005 20:29:26 -0500 Yun Mao yunmao@gmail.com wrote:
What's the right way to duplicate an array?
v = na.array(u)
v=u.copy()
Simon Burton wrote:
On Thu, 20 Jan 2005 20:29:26 -0500 Yun Mao yunmao@gmail.com wrote:
- Is there a way to do Matlab style slicing? e.g. if I have
i = array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y = x(i) would give me [1.1, 3.3]
have a look at the "take" method.
or use numarray:
import numarray as N i = N.array([0, 2]) x = N.array([1.1, 2.2, 3.3, 4.4]) y = x[i] y
array([ 1.1, 3.3])
Chris Barker wrote:
Simon Burton wrote:
On Thu, 20 Jan 2005 20:29:26 -0500 Yun Mao yunmao@gmail.com wrote:
- Is there a way to do Matlab style slicing? e.g. if I have i =
array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y = x(i) would give me [1.1, 3.3]
have a look at the "take" method.
or use numarray:
import numarray as N i = N.array([0, 2]) x = N.array([1.1, 2.2, 3.3, 4.4]) y = x[i] y
array([ 1.1, 3.3])
Or use scipy:
from scipy import * alter_numeric()
i = array([0,2]) x = array([1.1,2.2,3.3,4.4]) y = x[i]
print y [1.1 3.3]
On Fri, 21 Jan 2005, Travis Oliphant apparently wrote:
from scipy import * alter_numeric() i = array([0,2]) x = array([1.1,2.2,3.3,4.4]) y = x[i]
This ^ gives me an invalid index error. scipy version 0.3.0_266.4242
Alan Isaac
Alan G Isaac wrote:
On Fri, 21 Jan 2005, Travis Oliphant apparently wrote:
from scipy import * alter_numeric() i = array([0,2]) x = array([1.1,2.2,3.3,4.4]) y = x[i]
This ^ gives me an invalid index error. scipy version 0.3.0_266.4242
Travis's example works for me at scipy 0.3.2_302.4549 (from CVS), Numeric 23.6, numarray 1.1.1, all on FC3.
Alan G Isaac wrote:
On Fri, 21 Jan 2005, Travis Oliphant apparently wrote:
from scipy import * alter_numeric() i = array([0,2]) x = array([1.1,2.2,3.3,4.4]) y = x[i]
This ^ gives me an invalid index error. scipy version 0.3.0_266.4242
Your version of scipy is apparently too low.
Mine is 0.3.2_299.4506
-Travis
On 21.01.2005, at 02:29, Yun Mao wrote:
- When I do v = u[:, :], it seems u and v still point to the same
memory. e.g. When I do v[1,1]=0, u[1,1] will be zero out as well. What's the right way to duplicate an array? Now I have to do v = dot(u, identity(N)), which is kind of silly.
There are several ways to make a copy of an array. My personal preference is
import copy v = copy(u)
because this is a general mechanism that works for all Python objects.
- Is there a way to do Matlab style slicing? e.g. if I have
i = array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y = x(i) would give me [1.1, 3.3] Now I'm using map, but it gets a little annoying when there are two dimensions. Any ideas?
y = Numeric.take(x, i)
Konrad. -- ------------------------------------------------------------------------ ------- Konrad Hinsen Laboratoire Leon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France Tel.: +33-1 69 08 79 25 Fax: +33-1 69 08 82 61 E-Mail: hinsen@llb.saclay.cea.fr ------------------------------------------------------------------------ -------
On Jan 21, 2005, at 9:48, konrad.hinsen@laposte.net wrote:
There are several ways to make a copy of an array. My personal preference is
import copy v = copy(u)
That's of course
import copy v = copy.copy(u)
or
from copy import copy v = copy(u)
Konrad. -- --------------------------------------------------------------------- Konrad Hinsen Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France Tel.: +33-1 69 08 79 25 Fax: +33-1 69 08 82 61 E-Mail: hinsen@llb.saclay.cea.fr ---------------------------------------------------------------------
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Yun Mao