[Numpy-discussion] Changing a matrix element into a scalar
Alan G Isaac
alan.isaac@gmail....
Tue Aug 3 13:44:07 CDT 2010
On 8/3/2010 1:29 PM, Joshua Holbrook wrote:
> What's the
> advantage of the matrix datatype?
As it turns out, that's a controversial question. ;-)
One answer: pedagogy (for those used to matrices).
A related answer: succinctness and readability of *some* code.
>>> a,b,c = np.array([[1,2,3]]), np.array([[4],[5],[6]]), np.arange(9).reshape((3,3))
>>> d = np.dot(b,np.dot(a,c)) # matrix multiplication
>>> d2 = b.dot(a.dot(c)) # NumPy 1.5+
>>> d5 = d.dot(d).dot(d).dot(d).dot(d) #matrix exponentiation
>>> d[0,0] = 0
>>> di = np.linalg.inv(d) #matix inverse
>>> A,B,C = np.mat('1 2 3'), np.mat('4;5;6'), np.mat(np.arange(9).reshape((3,3)))
>>> D = B * (A * C) #matrix multiplication
>>> D5 = D**5 #matrix exponentiation
>>> D[0,0] = 0
>>> DI = D.I #matix inverse
fwiw,
Alan Isaac
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