[SciPy-User] array of matrices

Gustavo Goretkin gustavo.goretkin@gmail....
Fri Nov 25 16:14:14 CST 2011


I want to create an array, call it R, of matrices [M1,M2, M3, ...] . So R is 3D.

If v is a (column) vector, then np.dot(M1,v) matrix-multiples v by M1,
and produces another (column) vector. I want R to be shaped so that
np.dot(R,v) produces an array of column vectors [M1*v, M2*v, M3*v,
...]

Specifically, I want to define a function that resembles:

def rot_2d(theta):
    return np.array([[np.cos(theta), -np.sin(theta)],
                     [np.sin(theta), np.cos(theta)]])

that works even if theta itself is an array.

np.dot(rot_2d(np.array([0,np.pi/2,np.pi]),np.array([1,0]) produces an
array like [ [1,0], [0,1], [-1,0] ].

Thanks!
Gustav


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