[Tutor] summing arrays, along a dimension

[John]

 d
array([[0, 0, 1],
   [1, 2, 3],
   [2, 2, 4],
   [3, 6, 8]])
 e=reshape((d[:,-2]+d[:,-1]),(4,1))
 e
array([[ 1],
   [ 5],
   [ 6],
   [14]])

is there a better way to accomplish this?
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Re: [Tutor] summing arrays, along a dimension

[Ricardo Aráoz]

John wrote:
 d
 array([[0, 0, 1],
[1, 2, 3],
[2, 2, 4],
[3, 6, 8]])
 e=reshape((d[:,-2]+d[:,-1]),(4,1))
 e
 array([[ 1],
[ 5],
[ 6],
[14]])
  
 is there a better way to accomplish this?
 

 d
[[0, 0, 1], [1, 2, 3], [2, 2, 4], [3, 6, 8]]
 e = [sum(i) for i in d]
 e
[1, 6, 8, 17]
 f = [sum([L[i] for L in d]) for i in xrange(len(d[0]))]
 f
[6, 10, 16]
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Re: [Tutor] summing arrays, along a dimension

[Alan Gauld]

John [EMAIL PROTECTED] wrote 

 d
 array([[0, 0, 1],
   [1, 2, 3],
   [2, 2, 4],
   [3, 6, 8]])
 e=reshape((d[:,-2]+d[:,-1]),(4,1))
 e
 array([[ 1],
   [ 5],
   [ 6],
   [14]])
 
 is there a better way to accomplish this?

Better? Maybe. More readable I think is:

e1 = [ [row[-2]+row[-1]]  for row in d ]

You can convert the 2D list to an array object if you want later


Alan G.

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Re: [Tutor] summing arrays, along a dimension

[bob gailer]

John wrote:
  d
 array([[0, 0, 1],
[1, 2, 3],
[2, 2, 4],
[3, 6, 8]])
  e=reshape((d[:,-2]+d[:,-1]),(4,1))
  e
 array([[ 1],
[ 5],
[ 6],
[14]])
  
 is there a better way to accomplish this?
Which module are you using?

In APL we'd write +/d to reduce along the rows using +. Does the array 
object have a similar reduce method?

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