[Numpy-discussion] Boolean indexing
Sam Tygier
Sam.Tygier@hep.manchester.ac...
Tue Mar 8 07:59:32 CST 2011
Hi
I am having an issue with boolean slicing. it seems to work fine for
reading a value, but I can use it to set a value:
import numpy
b = numpy.array([[1,2],[3,4],[5,6],[7,8],[9,10]])
m = numpy.array([0,1,0,0,0], dtype=bool)
print b[m]
print b[m][0,0]
b[m][0,0] = -1
print b[m][0,0]
I think the boolean slicing is making a copy instead of a view. is there
a way around this?
My full problem is to modify a column of a rec array, if another column
has a condition. ie, a neat way of doing
for n in xrange(len(a)):
if a[n]['name'] == "foo":
a[n]['x'] += 1
i have been trying things like:
a[a[n]['name'] == "foo"]['x'] += 1
but does not work.
I am using
Python version 2.7 (r27:82500, Sep 16 2010, 18:02:00)
numpy 1:1.4.1-6.fc14 (fedora package)
Thanks
Sam
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