Hello,
I am trying to extract a column from a 2D array here is what is have
done:
--------------------------------------------
In [3]: a = array([[1,2,3],[1,2,3]])
In [4]: a
Out[4]:
array([[1, 2, 3],
[1, 2, 3]])
In [5]: a[:, 1]
Out[5]: array([2, 2])
In [6]: a[:, 1:2]
Out[6]:
array([[2],
[2]])
--------------------------------------------
when i use a[:, 1] i get a 1x2 array where as when i use a[:, 1:2] i get
a 2x1 array. The intuitive behavior of a[:, 1] should be a 2x1 array. Am
i doing something wrong here or is there some reason for this behavior ?
The behaviour is expected. a[:,1] is returned with one less dimension, just as for a one dimensional array b[1] is zero dimensional (a scalar). For instance
In [65]: int64(2).shape
Out[65]: ()
In [67]: a = mat(arange(6).reshape(2,3))
In [68]: a[:,1]
Out[68]:
matrix([[1],
[4]])
But generally it is best to just use arrays and get used to the conventions.
regards,
Rahul
Chuck
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