[Scipy-tickets] [SciPy] #1872: Ties in data leads to sqrt of a -ve number in wilcoxon test

SciPy Trac scipy-tickets@scipy....
Fri Mar 22 11:03:10 CDT 2013


#1872: Ties in data leads to sqrt of a -ve number in wilcoxon test
-------------------------+--------------------------------------------------
 Reporter:  simonb       |       Owner:  rgommers   
     Type:  defect       |      Status:  new        
 Priority:  normal       |   Milestone:  Unscheduled
Component:  scipy.stats  |     Version:  0.9.0      
 Keywords:               |  
-------------------------+--------------------------------------------------
 {{{
 import numpy
 import scipy.stats
 numpy.seterr(all='raise')
 # Raises: FloatingPointError: invalid value encountered in sqrt
 scipy.stats.wilcoxon([0.1] * 10)
 }}}

 Fails calculating "se = sqrt((count*V - T*T)/(count-1.0))".  In this
 example, the value passed to sqrt is -443.05555555555554.

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1872>
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