Python Error : the truth value of an array with more than one element is ambiguous. use a.any() or a.all()

Question

I want to compare item in list, this is my code:

for i in range(200):
        if g[i]==1 and d[4]==1:
           TP += 1
        elif g[i]==1 and d[4]==0:
           FP += 1
        elif g[i]==0 and d[4]==1:
           FN += 1
        elif g[i]==0 and d[4]==0:
           TN += 1

and I got this Error :

the truth value of an array with more than one element is ambiguous. use a.any() or a.all()

I don't know how to use the syntax as recommended above, how to solve it, thanks.

Solved it, actually it's not logical operator error, I forget that d is 2 dimensional array — mfathirirhas, Apr 19 '16 at 11:00
2 dimensional array? does python have array? are you using external module? — shahkalpesh, Apr 19 '16 at 11:03
'd' is 2d array, but I was accessing it like 1d array(look at code above), that's the problem, solved now. — mfathirirhas, Apr 19 '16 at 11:09

score 3 · Accepted Answer · edited May 23 '17 at 12:18

3

As mentioned by the author in comments, d is a 2-dimensional Numpy array.

The answer to that question explains that comparing multidimensional arrays in Numpy requires to the kind of comparison you want to perform (either any element is bitwise true or all elements are bitwise true).
That is the reason why you have to specify which kind of comparison you want, with (g[i] - d[4]).any() or (g[i] - d[4]).all().

edited May 23 '17 at 12:18

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answered Apr 19 '16 at 11:07

filaton

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solved it, actually it's not logical operator error, but I was accessing 2d array like 1d array, soved. – mfathirirhas Apr 19 '16 at 11:10

Python Error : the truth value of an array with more than one element is ambiguous. use a.any() or a.all()

1 Answers1