[Numpy-discussion] u in [u+1]
I'm having some trouble here. I have a list of numpy arrays. I want to know if an array 'u' is in the list. As an example, u = np.arange(10) : u not in [u+1] --- ValueErrorTraceback (most recent call last) /home/nbecker/raysat/test/ipython console in module() ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() What would be the way to do this? ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] u in [u+1]
I'm having some trouble here. I have a list of numpy arrays. I want to know if an array 'u' is in the list. Try: any(numpy.all(u == l) for l in array_list) standard caveats about float comparisons apply; perhaps any(numpy.allclose(u, l) for l in array_list) is more appropriate in certain circumstances. Can of course replace the first 'any' with 'all' or 'sum' to get different kinds of information, but using 'any' is equivalent to the 'in' query that you wanted. Why the 'in' operator below fails is that behind the scenes, 'u not in [u+1]' causes Python to iterate through the list testing each element for equality with u. Except that as the error states, arrays don't support testing for equality because such tests are ambiguous. (cf. many threads about this.) Zach On Feb 5, 2010, at 6:47 AM, Neal Becker wrote: I'm having some trouble here. I have a list of numpy arrays. I want to know if an array 'u' is in the list. As an example, u = np.arange(10) : u not in [u+1] --- ValueErrorTraceback (most recent call last) /home/nbecker/raysat/test/ipython console in module() ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() What would be the way to do this? ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] u in [u+1]
On Fri, Feb 5, 2010 at 8:48 AM, Zachary Pincus zachary.pin...@yale.edu wrote: I'm having some trouble here. I have a list of numpy arrays. I want to know if an array 'u' is in the list. Try: any(numpy.all(u == l) for l in array_list) standard caveats about float comparisons apply; perhaps any(numpy.allclose(u, l) for l in array_list) is more appropriate in certain circumstances. Can of course replace the first 'any' with 'all' or 'sum' to get different kinds of information, but using 'any' is equivalent to the 'in' query that you wanted. Why the 'in' operator below fails is that behind the scenes, 'u not in [u+1]' causes Python to iterate through the list testing each element for equality with u. Except that as the error states, arrays don't support testing for equality because such tests are ambiguous. (cf. many threads about this.) Zach On Feb 5, 2010, at 6:47 AM, Neal Becker wrote: I'm having some trouble here. I have a list of numpy arrays. I want to know if an array 'u' is in the list. As an example, u = np.arange(10) : u not in [u+1] --- ValueError Traceback (most recent call last) /home/nbecker/raysat/test/ipython console in module() ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() What would be the way to do this? maybe np.in1d(u, u+1) or np.in1d(u,u+1).all() is what you want help(np.in1d) Help on function in1d in module numpy.lib.arraysetops: in1d(ar1, ar2, assume_unique=False) Test whether each element of a 1D array is also present in a second array. Returns a boolean array the same length as `ar1` that is True where an element of `ar1` is in `ar2` and False otherwise. Josef ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
