Is it correct to add booleans in order to count the number of true values in a vector?

Posted by gerrit on Programmers See other posts from Programmers or by gerrit
Published on 2012-10-19T22:36:52Z Indexed on 2012/10/19 23:19 UTC
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Is it conceptually correct to sum a vector of booleans? From a mathematical point of view, I would argue it's not: True + True != 2. But it's quite practical to do so still! Example using the vectorised Python library numpy:

In [1]: X = rand(10)

In [2]: large = X>0.6

In [3]: large.dtype
Out[3]: dtype('bool')

In [4]: large.sum()
Out[4]: 7

I don't like it, but it's very practical. Is this a good practice?

Update: the aim is to count the number of true values in a vector.

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