On 18 October 2011 13:56, Chao YUE <chaoyue...@gmail.com> wrote: > but it's strange that if you use b[...,-1], > you get: > In [402]: b[...,-1] > Out[402]: array([ 9, 19]) > > if use b[...,-4:-1], > you get: > Out[403]: > array([[ 6, 7, 8], > [16, 17, 18]])
That's because you're mixing two different indexing constructs. In the first case, you're using direct indexing, so you get the values in b at the index you specify. In the second example you're using slicing syntax, where you get the values in b at the range of indices starting with -4 and ending *one before* -1 i.e. the values at b[..., -2]. Here's a simpler example: In [1]: a = range(5) In [2]: a Out[2]: [0, 1, 2, 3, 4] In [3]: a[0] Out[3]: 0 In [4]: a[2] Out[4]: 2 In [5]: a[0:2] Out[5]: [0, 1] In [6]: a[-3] Out[6]: 2 In [7]: a[-1] Out[7]: 4 In [8]: a[-3:-1] Out[8]: [2, 3] Cheers, Scott _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
