I have a numpy 2d array:
[[1,1,1],
[1,1,1],
[1,1,1],
[1,1,1]]
How can I get it so that it multiplies the indices from top to bottom with the corresponding values from a 1d array when the row length of the 2d array is smaller than length of 1d array ? For example multiply above with this:
[10, 20, 30, 40]
to get this:
[[10, 10, 10],
[20, 20, 20],
[30, 30, 30]
[40, 40, 40]]
Probably a duplicate, but I couldnt find exact thing I am looking for. Thanks in advance.
* in numpy does element-wise multiplication, for example multiply 1d array by another 1d array:
In [52]: np.array([3,4,5]) * np.array([1,2,3])
Out[52]: array([ 3, 8, 15])
When you multiply a 2d array by 1d array, same thing happens for every row of 2d array:
In [53]: np.array([[3,4,5],[4,5,6]]) * np.array([1,2,3])
Out[53]:
array([[ 3, 8, 15],
[ 4, 10, 18]])
For your specific example:
In [66]: ones = np.ones(12, dtype=np.int).reshape(4,3)
In [67]: a = np.array([10, 20, 30, 40])
In [68]: (ones.T * a).T
Out[68]:
array([[10, 10, 10],
[20, 20, 20],
[30, 30, 30],
[40, 40, 40]])
