[Numpy-discussion] mixing arrays and matrices: squeeze yes, flattened no?

Christopher Barker Chris.Barker at noaa.gov
Tue Feb 21 12:49:02 CST 2006


Travis Oliphant wrote:

> You can mix arrays and matrices just fine if you remember that 1d arrays 
> are equivalent to row-vectors.

and you can easily get a column vector out of an array, if you remember 
that you want to keep it 2-d. i.e. use a slice rather than an index:

 >>> import numpy as N
 >>> a = N.ones((5,10))
 >>> a[:,1].shape # an index: it reduces the rank
(5,)
 >>> a[:,1:2].shape # a slice: it keeps the rank
(5, 1)

-Chris







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Christopher Barker, Ph.D.
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