[Numpy-discussion] Logical Selector

Geoffrey Zhu gzhu at peak6.com
Wed Jul 18 15:06:40 EDT 2007

Hi Everyone,

I am finding that numpy cannot operate on boolean arrays. For example,
the following does not work:


x[x[:,0]>x[:,1] and x[1:]>1,:]

It gives me an syntax error:

Traceback (most recent call last):
  File "<pyshell#74>", line 1, in <module>
    x[x[:,0]>x[:,1] and x[1:]>1,:]
ValueError: The truth value of an array with more than one element is
ambiguous. Use a.any() or a.all()

However, this is not what I want. I want a "piece-wise" "AND" operation
on the two boolean vectors. In other words, the row is selected if both
are true. How do I accomplish this?

Many thanks,

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