[SciPy-user] concatenation of arrays woes !!
Karthikesh Raju
karthik at james.hut.fi
Tue May 4 11:19:55 CDT 2004
Hi Gary and others,
thankx for your reply. i had managed to break the procedure into bits and
pieces and get the work done. i have attached the file. Is there some way
by which we can efficiently do something like
s2 = s[0:CL-d[k,l],k]
s3 = concatenate(z1,z2,s2[:,NewAxis])
stemp[:,NewAxis] = s3
is there any means by which i can avoid having s2 as a variable, and by
using the NewAxis during striding process itself.
i have just built this matrix now, row by row :), any way to improve this!
With warm regards
karthik
-----------------------------------------------------------------------
Karthikesh Raju, email: karthik at james.hut.fi
Researcher, http://www.cis.hut.fi/karthik
Helsinki University of Technology, Tel: +358-9-451 5389
Laboratory of Comp. & Info. Sc., Fax: +358-9-451 3277
Department of Computer Sc.,
P.O Box 5400, FIN 02015 HUT,
Espoo, FINLAND
-----------------------------------------------------------------------
On Tue, 4 May 2004, Gary Pajer wrote:
> ----- Original Message -----
> From: "Karthikesh Raju" <karthik at james.hut.fi>
> To: <scipy-user at scipy.net>
> Sent: Tuesday, May 04, 2004 4:10 AM
> Subject: [SciPy-user] concatenation of arrays woes !!
>
>
> >
> > Hi All,
> >
> > is it possible to concatenate arrays along the column,
> >
> > A[:,1:5] = concatenate(a,b,c)
> > a is 2x1, b 2x1, c 1x1
> >
> > i have been trying to convert the following matlab code and this is my
> > stumbling block for several months :(
> >
> > K = 3
> > CL = 5
> > L = 2
> > d -- (K,L) in the range (0,CL)
> > codes -- (K,CL)
> > window = 1
> > s = codes'
> >
> > output S -(CL*window,K*L*(window+1)) matrix
> >
> > for k = 1:K
> > for l = 1:L
> > S(:,1+(window+1)*(l-1)+(window+1)*L*(k-1)) =
> > [s(CL-d(k,l)+1:CL,k);
> zeros(CL*(window-1),1);zeros(CL-d(k,l),1)]
> > S(:,(window+1)*1+(window+1)*L*(k-1)) =
> > [zeros(d(k,l),1);zeros(CL*(window-1),1);s(1:CL-d(k,l),k)]
> > for n=2:window
> > S(:,n+(window+1)*(l-1)+(numbits+1)*L*(k-1)) =
> > [zeros(d(k,l),1); zeros(CL*(n-2),1);
> > s(:,k);zeros((window-n)*CL+CL-d(k,l),1)]
> > end
> > end
> > end
> >
> > --------------------
> >
> > This module has been my stumbling block for the last 2 months, had no
> > problems with matlab, here i have all kinds of concatination woes. Please
> > give me pointers on how to achieve such concatenations,
> >
> > thanks a lot
> >
> > regards
> > karthik
>
>
>
> I'm still not sure what you are trying to achieve. If you post a minimal
> contrived example of what you are trying to do instead of a clip from the
> middle of your code it would be easier to figure out.
>
> But have you explored r_[ ] and c_[ ] ? ('c' for column, 'r' for row)
> These constructions are designed to aid concatenation:
>
> >>> from scipy import *
> >>> x=array([1,2])
> >>> y=array([3,4])
>
> >>> c_[x,y]
> array([1, 2, 3, 4])
>
> >>> c_[x[:,NewAxis],y[:,NewAxis]]
> array([[1, 3],
> [2, 4]])
>
> >>> r_[x[:,NewAxis],y[:,NewAxis]]
> array([[1],
> [2],
> [3],
> [4]])
>
>
> hth,
> gary
>
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> SciPy-user at scipy.net
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>
>
-------------- next part --------------
from numarray import *
K = 3
L = 2
CL = 5
codes = arange(1,16,shape=(K,CL))
codes.transpose()
s = array(codes, copy=1)
print s
d = ones((K,L))
window = 1
S = zeros([CL*window,K*L*(window+1)])
for k in range(K):
for l in range(L):
print "--"*30 + "\n"
# first row
#--------------------------------------------------
stemp = S[:,(window+1)*(l)+(window+1)*L*(k)]
s2 = s[CL-d[k,l]:CL,k]
z1 = zeros([CL*(window-1),1])
z2 = zeros([CL-d[k,l],1])
if CL*(window-1) == 0:
s3 = concatenate((s2[:,NewAxis],z2))
else:
s3 = concatenate((s2[:,NewAxis],z1,z2))
stemp[:,NewAxis] = s3
#--------------------------------------------------
# # second row
#--------------------------------------------------
stemp = S[:,(window+1)*l+window+(window+1)*L*k]
z1 = zeros([d[k,l],1]);
z2 = zeros([CL*(window-1),1])
s2 = s[0:CL-d[k,l],k]
if CL*(window-1) == 0:
s3 = concatenate((z1,s2[:,NewAxis]))
else:
s3 = concatenate((z1,z2,s2[:,NewAxis]))
stemp[:,NewAxis] = s3
#--------------------------------------------------
# final push
for w in range(0,window-1):
stemp = S[:,w+1+(window+1)*l+(window+1)*L*k]
z1 = zeros([d[k,l],1])
z2 = zeros([CL*w,1])
s2 = s[:,k]
z3 = zeros([(window-(w+2))*CL+CL-d[k,l],1])
if CL*w == 0:
s3 = concatenate((z1,s2[:,NewAxis],z3))
else:
s3 = concatenate((z1,z2,s2[:,NewAxis],z3))
print s3
stemp[:,NewAxis] = s3
print S
print S.shape
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