[Rd] scale(x, center=FALSE) (PR#14219)
mrizzo at bgsu.edu
mrizzo at bgsu.edu
Mon Feb 22 04:30:11 CET 2010
Full_Name: Maria Rizzo
Version: 2.10.1 (2009-12-14)
OS: Windows XP SP3
Submission from: (NULL) (72.241.75.222)
platform i386-pc-mingw32
arch i386
os mingw32
system i386, mingw32
status
major 2
minor 10.1
year 2009
month 12
day 14
svn rev 50720
language R
version.string R version 2.10.1 (2009-12-14)
scale returns incorrect values when center=FALSE and scale=TRUE.
When center=FALSE, scale=TRUE, the "scale" used is not the square root of sample
variance, the "scale" attribute is equal to sqrt(sum(x^2)/(n-1)).
Example:
x <- runif(10)
n <- length(x)
scaled <- scale(x, center=FALSE, scale=TRUE)
scaled
s.bad <- attr(scaled, "scale")
s.bad #wrong
sd(x) #correct
#compute the sd as if data has already been centered
#that is, compute the variance as sum(x^2)/(n-1)
sqrt(sum(x^2)/(n-1))
More information about the R-devel
mailing list