[NumPy-Tickets] [NumPy] #1564: numpy.arange returns array with wrong length

NumPy Trac numpy-tickets@scipy....
Wed Jul 28 15:01:33 CDT 2010


#1564: numpy.arange returns array with wrong length
-------------------------+--------------------------------------------------
  Reporter:  crassus     |       Owner:  somebody     
      Type:  defect      |      Status:  closed       
  Priority:  high        |   Milestone:  1.5.0        
 Component:  numpy.core  |     Version:  1.3.0        
Resolution:  invalid     |    Keywords:  arange length
-------------------------+--------------------------------------------------
Changes (by pv):

  * status:  new => closed
  * resolution:  => invalid


Comment:

 The result from `arange` is defined as: numbers between [start, stop),
 spaced by step.

 What you are seeing is a consequence of inexact floating point arithmetic.
 {{{
 >>> from math import ceil
 >>> step = 1.0/400000
 >>> stop = 971 * step
 >>> stop/step
 971.00000000000011
 }}}
 There are 972 numbers fitting in the interval.

 You should use `numpy.linspace`, if you want a given number of equally
 spaced items.

-- 
Ticket URL: <http://projects.scipy.org/numpy/ticket/1564#comment:1>
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