R help - Jan 2008 - question about scale() function

Hi,

The documentation for scale() states:"If center is TRUE then centering is
done by subtracting the column means (omitting NAs) of x from their
corresponding columns". But it seems that R is subtracting something else
instead of the column mean:
> x=c(2,4,3,4,5)
> mean(x)
[1] 3.6
> x-mean(x)
[1] -1.6  0.4 -0.6  0.4  1.4
> scale(x)
           [,1]
[1,] -1.4032928
[2,]  0.3508232
[3,] -0.5262348
[4,]  0.3508232
[5,]  1.2278812
attr(,"scaled:center")
[1] 3.6
attr(,"scaled:scale")
[1] 1.140175

Notice that -1.4 is not the same as -1.6, and 1.2 is not the same as 1.4,
etc. Does anyone know what exactly is scale() doing if it is not subtracting
the column mean? Thanks.

-- 
Tom

	[[alternative HTML version deleted]]

Never mind. I forgot the scale= parameter.

On 1/3/08, tom soyer <tom.soyer@gmail.com> wrote:
>
> Hi,
>
> The documentation for scale() states:"If center is TRUE then centering
is
> done by subtracting the column means (omitting NAs) of x from their
> corresponding columns". But it seems that R is subtracting something
else
> instead of the column mean:
>
> > x=c(2,4,3,4,5)
> > mean(x)
> [1] 3.6
> > x-mean(x)
> [1] -1.6  0.4 -0.6  0.4  1.4
> > scale(x)
>            [,1]
> [1,] -1.4032928
> [2,]  0.3508232
> [3,] -0.5262348
> [4,]  0.3508232
> [5,]  1.2278812
> attr(,"scaled:center")
> [1] 3.6
> attr(,"scaled:scale")
> [1] 1.140175
>
> Notice that -1.4 is not the same as -1.6, and 1.2 is not the same as 1.4,
> etc. Does anyone know what exactly is scale() doing if it is not
subtracting
> the column mean? Thanks.
>
> --
> Tom
>


-- 
Tom

	[[alternative HTML version deleted]]

Does this give you what you want?
> x=c(2,4,3,4,5)
> ?scale
> scale(x,scale=FALSE)
     [,1]
[1,] -1.6
[2,]  0.4
[3,] -0.6
[4,]  0.4
[5,]  1.4
attr(,"scaled:center")
[1] 3.6
>
Default is to performance scaling: "If scale is TRUE then scaling is
done by dividing the (centered) columns of x by their
root-mean-square, and if scale is FALSE, no scaling is done. "

On Jan 3, 2008 9:37 PM, tom soyer <tom.soyer at gmail.com>
wrote:
> Hi,
>
> The documentation for scale() states:"If center is TRUE then centering
is
> done by subtracting the column means (omitting NAs) of x from their
> corresponding columns". But it seems that R is subtracting something
else
> instead of the column mean:
>
> > x=c(2,4,3,4,5)
> > mean(x)
> [1] 3.6
> > x-mean(x)
> [1] -1.6  0.4 -0.6  0.4  1.4
> > scale(x)
>           [,1]
> [1,] -1.4032928
> [2,]  0.3508232
> [3,] -0.5262348
> [4,]  0.3508232
> [5,]  1.2278812
> attr(,"scaled:center")
> [1] 3.6
> attr(,"scaled:scale")
> [1] 1.140175
>
> Notice that -1.4 is not the same as -1.6, and 1.2 is not the same as 1.4,
> etc. Does anyone know what exactly is scale() doing if it is not
subtracting
> the column mean? Thanks.
>
> --
> Tom
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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