[Numpy-discussion] Array mapping question
Jorge Scandaliaris
jorgesmbox-ml@yahoo...
Tue Mar 16 07:00:59 CDT 2010
Hi,
I have a 1D array containing indexes to specific measurements. As this array is
a slice of a bigger one, the indexes don't necessarily start at 0 nor they are
sequential. For example, I can have an array A where
In [34]: A.shape
Out[34]: (4764,)
In [35]: ctab = np.unique(A)
In [36]: ctab
Out[36]: array([48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62],
dtype=int64)
I would like to map these indexes to a sequence starting from zero. The usual
look up table approach doesn't work here. I can solve this using a dictionary,
but then I am forced to using a loop or a list comprehension:
In [38]: cdic = dict(zip(ctab, range(ctab.size)))
In [39]: cdic
Out[39]:
{48: 0,
49: 1,
50: 2,
51: 3,
52: 4,
53: 5,
54: 6,
55: 7,
56: 8,
57: 9,
58: 10,
59: 11,
60: 12,
61: 13,
62: 14}
A_remapped = np.asarray([cdic[x] for x in A])
Am I overlooking a better way of doing this?
Thanks,
Jorge
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