thanks Scott. very good explanation. cheers,
Chao 2011/10/18 Scott Sinclair <scott.sinclair...@gmail.com> > 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 > -- *********************************************************************************** Chao YUE Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL) UMR 1572 CEA-CNRS-UVSQ Batiment 712 - Pe 119 91191 GIF Sur YVETTE Cedex Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16 ************************************************************************************
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