[NumPy-Tickets] [NumPy] #1980: Matrix A from zeros, after changing values, yields strange A*A.T behavior
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Wed Nov 16 18:15:47 CST 2011
#1980: Matrix A from zeros, after changing values, yields strange A*A.T behavior
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Reporter: ehassler | Owner: somebody
Type: defect | Status: new
Priority: normal | Milestone: Unscheduled
Component: Other | Version: 1.6.0
Keywords: |
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Comment(by warren.weckesser):
This has nothing to do with zeros(). In your sample code, P0 is an
ndarray, but P1 is a matrix object. Multiplication of ndarrays is
element-wise, not algebraic. To perform the algebraic product of two
ndarrays, use the dot() method (or the numpy.dot() function).
Multiplication of matrix objects, however, is defined to be the usual
algebraic matrix product. So you want this comparison in your script
(which will print True):
{{{
print numpy.all(P0.dot(P0.T) == P1*P1.T)
}}}
--
Ticket URL: <http://projects.scipy.org/numpy/ticket/1980#comment:1>
NumPy <http://projects.scipy.org/numpy>
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