Code:
n=3
x=np.fromfunction(lambda i,j: (i==1)and(j==1), (n,n), dtype=int)
leads to "ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()"
What's the problem?
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1 Answer
The documentation is misleading. The function isn't called repeatedly with the indices of each individual cell; it's called once, with index arrays representing the indices of all the cells at once. The return value of this one function call is returned directly:
>>> numpy.fromfunction(lambda *args: 1, (2, 2))
1
>>> numpy.fromfunction(lambda *args: args, (2, 2))
(array([[ 0., 0.],
[ 1., 1.]]), array([[ 0., 1.],
[ 0., 1.]]))
You'll need to change your function to operate that way:
lambda i, j: (i==1) & (j==1)
# ^ elementwise bitwise and
1 Comment
Ymareth
I would second the statement "The documentation is misleading.".