What does the c underscore expression `c_` do exactly?
numpy, python
Solution
Use IPython's `?` syntax to get more information:
In [2]: c_?
Type: CClass
Base Class: <class 'numpy.lib.index_tricks.CClass'>
String Form:<numpy.lib.index_tricks.CClass object at 0x9a848cc>
Namespace: Interactive
Length: 0
File: /usr/lib/python2.7/dist-packages/numpy/lib/index_tricks.py
Docstring:
Translates slice objects to concatenation along the second axis.
This is short-hand for ``np.r_['-1,2,0', index expression]``, which is
useful because of its common occurrence. In particular, arrays will be
stacked along their last axis after being upgraded to at least 2-D with
1's post-pended to the shape (column vectors made out of 1-D arrays).
For detailed documentation, see `r_`.
Examples
--------
>>> np.c_[np.array([[1,2,3]]), 0, 0, np.array([[4,5,6]])]
array([[1, 2, 3, 0, 0, 4, 5, 6]])
Problem
It seems to be some kind of horizontal concatenation, but I could not find any documentation online. Here a minimal working example: ``` In [1]: from numpy import c_ In [2]: a = ones(4) In [3]: b = zeros((4,10)) In [4]: c_[a,b] Out[4]: array([[ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]]) ```