[R] compute the mean of two (or more) correlations

[Viechtbauer Wolfgang (STAT)]

And at that point, one is essentially doing a meta-analysis. For example:

library(metafor)

ri <- c(.5, .4)
ni <- c(40, 25)

res <- rma(ri=ri, ni=ni, measure="ZCOR", method="FE")
predict(res, transf=transf.ztor, digits=2)

 pred  se ci.lb ci.ub
 0.46  NA  0.24  0.64

You also get the CI (in addition to the back-transformed average).

Best,

Wolfgang

-- 
Wolfgang Viechtbauer 
Department of Psychiatry and Neuropsychology 
School for Mental Health and Neuroscience 
Maastricht University, P.O. Box 616 
6200 MD Maastricht, The Netherlands 
Tel: +31 (43) 368-5248 
Fax: +31 (43) 368-8689 
Web: http://www.wvbauer.com 


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Michael Dewey
> Sent: Tuesday, July 26, 2011 12:23
> To: Joshua Wiley; Martin Batholdy
> Cc: r-help at r-project.org
> Subject: Re: [R] compute the mean of two (or more) correlations
> 
> At 15:47 25/07/2011, Joshua Wiley wrote:
> >Hi Martin,
> >
> >Off hand I do not know of a pre-defined function to do it, but the
> >"z-transformation" is just the inverse hyperbolic function, the mean
> >is just the mean, and the back transformation is the hypoerbolic
> >function so...
> >
> >############
> >x <- c(.5, .4)
> >tanh(mean(atanh(x)))
> >############
> >
> >should do it.
> 
> Assuming the correlations are based on the same sample size as I
> would have thought one would otherwise have wanted to weight them.
> 
> 
> >Cheers,
> >
> >Josh
> >
> >On Mon, Jul 25, 2011 at 7:11 AM, Martin Batholdy
> ><batholdy at googlemail.com> wrote:
> > > Hi,
> > >
> > >
> > > is there a function in R that computes the mean of two (or more)
> > correlations?
> > > (that is doing the z-transformation of the correlations,
> > computing the mean of the z-values and then retransform it to a
> correlation).
> > >
> > > Or is there a fisher-table implemented?
> > >
> > >
> > > I have not found anything via help.search() or google so far.
> > >
> > >
> > > thank you!
> > > ______________________________________________
> > > 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.
> > >
> >
> >
> >
> >--
> >Joshua Wiley
> >Ph.D. Student, Health Psychology
> >University of California, Los Angeles
> >https://joshuawiley.com/
> 
> Michael Dewey
> info at aghmed.fsnet.co.uk
> http://www.aghmed.fsnet.co.uk/home.html
> 
> ______________________________________________
> 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.