R help - Jun 2010 - back transforming arcsine transformations in metafor

Hi everyone,

I'm using the metafor package to meta-analyze a set of proportions. This is
working really well for the raw proportions, but is there a way to
back-transform the arcsine transformed proportions in the rma or forest
functions with the atransf option? The estimates and CIs for the transformed
proportions need to be back-transformed to be the sin of the estimate squared.
Back-transforming the output isn't a big deal - it's the forest plots
that I would need the back transform for. Any help or advice would be greatly
appreciated.

Thanks in advance,
Chris

Dear Chris,

Just define the following function:

transf.iasin <- function(x) {
   z <- sin(x)^2
   return(z)
}

to give the inverse of the arcsine transformation. Then specify this function
under the atransf argument.

I will add the transf.iasin() function to the package.

Best,

--
Wolfgang Viechtbauer                        http://www.wvbauer.com/
Department of Methodology and Statistics    Tel: +31 (43) 388-2277
School for Public Health and Primary Care   Office Location:
Maastricht University, P.O. Box 616         Room B2.01 (second floor)
6200 MD Maastricht, The Netherlands         Debyeplein 1 (Randwyck)


----Original Message----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of Chris Miller Sent:
Thursday, June 10, 2010 00:28 To: r-help at r-project.org
Subject: [R] back transforming arcsine transformations in metafor
> Hi everyone,
>
> I'm using the metafor package to meta-analyze a set of proportions.
> This is working really well for the raw proportions, but is there a
> way to back-transform the arcsine transformed proportions in the rma
> or forest functions with the atransf option? The estimates and CIs
> for the transformed proportions need to be back-transformed to be the
> sin of the estimate squared. Back-transforming the output isn't a big
> deal - it's the forest plots that I would need the back transform
> for. Any help or advice would be greatly appreciated.
>
> Thanks in advance,
> Chris
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