[R-sig-eco] Log transforming zero value data

Philippe Grosjean phgrosjean at sciviews.org
Wed Jun 24 09:37:16 CEST 2009


See ?log1p
Best,

Philippe Grosjean
..............................................<°}))><........
  ) ) ) ) )
( ( ( ( (    Prof. Philippe Grosjean
  ) ) ) ) )
( ( ( ( (    Numerical Ecology of Aquatic Systems
  ) ) ) ) )   Mons-Hainaut University, Belgium
( ( ( ( (
..............................................................

Nate Upham wrote:
> I have a general stats question for you guys:
> 
> How does one normally deal with zero (0) values when log transforming data?  
> 
> I would like to log transform (natural log, ln) several response variables for use in quantile
> regression.  But one of my variables includes several zero values.  Since ln(0) = infinity, this is
> not readily possible.  Is it best to remove all data with zero values?  Or should I add a very small
> number to each value (e.g., 0.00001)?  This seems problematic.  Is there an easy way to address this
> issue?
> 
> Thanks much for your help,
> --Nate
> 
> _________________________________
> Nathan S. Upham
> Ph.D. student
> Committee on Evolutionary Biology
> University of Chicago
> 1025 E. 57th St., Culver 402
> Chicago, IL 60637
> nsupham at uchicago.edu
> 
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