Python Matrix, Any Solution?

MY input(just for example): from numpy import * x=[['1' '7'] ['1.5' '8'] ['2' '5.5'] ['2' '9']] I want to make next thing on random matrix: 1. for each row calculate: > f

Solution 1:

How about the following:

In [1]: import numpy as np

In [2]: x=np.array([[1, 7],[1.5, 8],[2, 5.5],[2, 9]])

In [3]: np.sum(np.outer(row,row) for row in x)
Out[3]: 
array([[  11.25,   48.  ],
       [  48.  ,  224.25]])

Solution 2:

First, you should create the matrix containing floating point numbers instead of strings:

x = numpy.array([[1, 7], [1.5, 8], [2, 5.5], [2, 9]])

Next, you can use NumPy's broadcasting rules to build the product matrices:

y = x[:, :, None] * x[:, None]

Finally, sum over all matrices:

print y.sum(axis=0)

printing

[[  11.25   48.  ]
 [  48.    224.25]]

Note that this solution avoids any Python loops.