[Numpy-discussion] indexing bug in numpy r2694

Keith Goodman kwgoodman at gmail.com
Wed Jun 28 12:26:03 CDT 2006


>> x = asmatrix(rand(3,2))

>> y = asmatrix(rand(3,1))

>> y

matrix([[ 0.77952062],
       [ 0.97110465],
       [ 0.77450218]])

>> idx = where(y > 0.5)[0]

>> idx
matrix([[0, 1, 2]])

>> x[idx,:]

matrix([[ 0.24837887,  0.52988253],
       [ 0.28661085,  0.43053076],
       [ 0.05360893,  0.22668509]])

So far everything works as it should. Now the problem:

>> y[idx,:]
---------------------------------------------------------------------------
exceptions.ValueError                                Traceback (most
recent call last)

/usr/local/lib/python2.4/site-packages/numpy/core/defmatrix.py in
__getitem__(self, index)
    120
    121     def __getitem__(self, index):
--> 122         out = N.ndarray.__getitem__(self, index)
    123         # Need to swap if slice is on first index
    124         retscal = False

/usr/local/lib/python2.4/site-packages/numpy/core/defmatrix.py in
__array_finalize__(self, obj)
    116             self.shape = (1,1)
    117         elif ndim == 1:
--> 118             self.shape = (1,self.shape[0])
    119         return
    120

ValueError: total size of new array must be unchanged


And, on a related note, shouldn't this be a column vector?

>> x[idx,0]
matrix([[ 0.24837887,  0.28661085,  0.05360893]])




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