On Wed, Feb 26, 2014 at 5:32 AM, Slavin, Jonathan <jsla...@cfa.harvard.edu>wrote:
> This behavior is a property of python slicing. It takes some getting used > to, but has its advantages. > quite a few, actually! They key with slicing is to think of the index as pointing to the space between the elements: 0 1 2 3 4 5 | | | | | | but the reason (and beauty) of this is that it results in a number of nifty properties: len( seq [i:j] ) == j-i seq[i:j] + seq[j:k] == seq[i:k] len( seq[:i] ) == i len( seq[-i:] ) == i and if you have an array representing a axis, for instance, and want to know the value of a given index: x = x_0 + i*dx or the index of a given value: i = (x - x_0) / dx Notice that I don't have a single +1 or -1 in all of that -- this make sit easier to undersand and a lot less error prone. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov
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