[R] Signs of loadings from princomp on Windows
Liaw, Andy
andy_liaw at merck.com
Tue Sep 14 18:55:32 CEST 2004
Ditto here, although not from a fresh session. Also 1.9.1 binary from CRAN,
on WinXPPro:
> library(MASS)
> data(painters)
> pca.painters <- princomp(painters[ ,1:4])
> loadings(pca.painters)
Loadings:
Comp.1 Comp.2 Comp.3 Comp.4
Composition 0.484 -0.376 0.784 -0.101
Drawing 0.424 0.187 -0.280 -0.841
Colour -0.381 -0.845 -0.211 -0.310
Expression 0.664 -0.330 -0.513 0.432
Comp.1 Comp.2 Comp.3 Comp.4
SS loadings 1.00 1.00 1.00 1.00
Proportion Var 0.25 0.25 0.25 0.25
Cumulative Var 0.25 0.50 0.75 1.00
> pca.painters <- princomp(painters[ ,1:4])
> loadings(pca.painters)
Loadings:
Comp.1 Comp.2 Comp.3 Comp.4
Composition -0.484 -0.376 0.784 -0.101
Drawing -0.424 0.187 -0.280 -0.841
Colour 0.381 -0.845 -0.211 -0.310
Expression -0.664 -0.330 -0.513 0.432
Comp.1 Comp.2 Comp.3 Comp.4
SS loadings 1.00 1.00 1.00 1.00
Proportion Var 0.25 0.25 0.25 0.25
Cumulative Var 0.25 0.50 0.75 1.00
Andy
> From: Sundar Dorai-Raj
>
> Hi all,
> I was able to replicate Francisco's observation. I'm using R-1.9.1
> installed from binaries on Windows 2000 Pro.
>
> [Previously saved workspace restored]
>
> > library(MASS)
> > data(painters)
> > pca.painters <- princomp(painters[ ,1:4])
> > loadings(pca.painters)
>
> Loadings:
> Comp.1 Comp.2 Comp.3 Comp.4
> Composition 0.484 -0.376 0.784 -0.101
> Drawing 0.424 0.187 -0.280 -0.841
> Colour -0.381 -0.845 -0.211 -0.310
> Expression 0.664 -0.330 -0.513 0.432
>
> Comp.1 Comp.2 Comp.3 Comp.4
> SS loadings 1.00 1.00 1.00 1.00
> Proportion Var 0.25 0.25 0.25 0.25
> Cumulative Var 0.25 0.50 0.75 1.00
> > pca.painters <- princomp(painters[ ,1:4])
> > loadings(pca.painters)
>
> Loadings:
> Comp.1 Comp.2 Comp.3 Comp.4
> Composition -0.484 -0.376 0.784 -0.101
> Drawing -0.424 0.187 -0.280 -0.841
> Colour 0.381 -0.845 -0.211 -0.310
> Expression -0.664 -0.330 -0.513 0.432
>
> Comp.1 Comp.2 Comp.3 Comp.4
> SS loadings 1.00 1.00 1.00 1.00
> Proportion Var 0.25 0.25 0.25 0.25
> Cumulative Var 0.25 0.50 0.75 1.00
> > R.version
> _
> platform i386-pc-mingw32
> arch i386
> os mingw32
> system i386, mingw32
> status
> major 1
> minor 9.1
> year 2004
> month 06
> day 21
> language R
>
> Francisco Chamu wrote:
>
> > I have run this on both Windows 2000 and XP. All I did was install
> > the binaries from CRAN so I think I am using the standard Rblas.dll.
> >
> > To reproduce what I see you must run the code at the
> beginning of the
> > R session. After the second run, all subsequent runs give the same
> > result as the second set.
> >
> > Thanks,
> > Francisco
> >
> >
> > On Tue, 14 Sep 2004 08:29:25 +0200, Uwe Ligges
> > <ligges at statistik.uni-dortmund.de> wrote:
> >
> >>Prof Brian Ripley wrote:
> >>
> >>>I get the second set each time, on Windows, using the
> build from CRAN.
> >>>Which BLAS are you using?
> >>
> >>
> >>Works also well for me with a self compiled R-1.9.1 (both
> with standard
> >>Rblas as well as with the Rblas.dll for Athlon CPU from CRAN).
> >>Is this a NT-based version of Windows (NT, 2k, XP)?
> >>
> >>Uwe
> >>
> >>
> >>
> >>
> >>
> >>>On Tue, 14 Sep 2004, Francisco Chamu wrote:
> >>>
> >>>
> >>>
> >>>>I start a clean session of R 1.9.1 on Windows and I run
> the following code:
> >>>>
> >>>>
> >>>>
> >>>>>library(MASS)
> >>>>>data(painters)
> >>>>>pca.painters <- princomp(painters[ ,1:4])
> >>>>>loadings(pca.painters)
> >>>>
> >>>>Loadings:
> >>>> Comp.1 Comp.2 Comp.3 Comp.4
> >>>>Composition 0.484 -0.376 0.784 -0.101
> >>>>Drawing 0.424 0.187 -0.280 -0.841
> >>>>Colour -0.381 -0.845 -0.211 -0.310
> >>>>Expression 0.664 -0.330 -0.513 0.432
> >>>>
> >>>> Comp.1 Comp.2 Comp.3 Comp.4
> >>>>SS loadings 1.00 1.00 1.00 1.00
> >>>>Proportion Var 0.25 0.25 0.25 0.25
> >>>>Cumulative Var 0.25 0.50 0.75 1.00
> >>>>
> >>>>However, if I rerun the same analysis, the loadings of the first
> >>>>component have the opposite sign (see below), why is that? I have
> >>>>read the note
> >>>>in the princomp help that says
> >>>>
> >>>> "The signs of the columns of the loadings and scores
> are arbitrary,
> >>>> and so may differ between different programs for PCA, and even
> >>>> between different builds of R."
> >>>>
> >>>>However, I still would expect the same signs for two runs
> in the same session.
> >>>>
> >>>>
> >>>>
> >>>>>pca.painters <- princomp(painters[ ,1:4])
> >>>>>loadings(pca.painters)
> >>>>
> >>>>Loadings:
> >>>> Comp.1 Comp.2 Comp.3 Comp.4
> >>>>Composition -0.484 -0.376 0.784 -0.101
> >>>>Drawing -0.424 0.187 -0.280 -0.841
> >>>>Colour 0.381 -0.845 -0.211 -0.310
> >>>>Expression -0.664 -0.330 -0.513 0.432
> >>>>
> >>>> Comp.1 Comp.2 Comp.3 Comp.4
> >>>>SS loadings 1.00 1.00 1.00 1.00
> >>>>Proportion Var 0.25 0.25 0.25 0.25
> >>>>Cumulative Var 0.25 0.50 0.75 1.00
> >>>>
> >>>>
> >>>>>R.version
> >>>>
> >>>> _
> >>>>platform i386-pc-mingw32
> >>>>arch i386
> >>>>os mingw32
> >>>>system i386, mingw32
> >>>>status
> >>>>major 1
> >>>>minor 9.1
> >>>>year 2004
> >>>>month 06
> >>>>day 21
> >>>>language R
> >>>>
> >>>>BTW, I have tried the same in R 1.9.1 on Debian and I
> can't reproduce
> >>>>what I see
> >>>>on Windows. In fact all the runs give the same as the
> second run on Windows.
> >>>>
> >>>>-Francisco
> >>>>
> >>>>______________________________________________
> >>>>R-help at stat.math.ethz.ch mailing list
> >>>>https://stat.ethz.ch/mailman/listinfo/r-help
> >>>>PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
> >>>>
> >>>>
> >>>
> >>>
>
> >>
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
>
> ______________________________________________
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