[R] combined value in forestplot function

David Scott d.scott at auckland.ac.nz
Wed Aug 19 01:11:06 CEST 2009

carol white wrote:
> Hi,
> How is the combined value (displayed by a diamond on the forest plot) of a meta-analysis illustrated by a forest plot calculated? The applied method and all calculation details are welcome.
> Thanks
> Carol

This is not a very well posed question. First of all there are two ways 
of getting a diamond in a forest plot, using either fixed or random 
effects meta analysis. Secondly there are at least two R packages which 
do meta-analysis, meta and rmeta. To which are you referring? They may 
do something a little different.

Despite this you can find the answer yourself by looking at the code. 
For example in the package rmeta, you probably need to look at the code 
for meta.DSl and meta.MH for the calculation of (respectively) random 
and fixed meta-analyses.

If you can't see what the code is doing and perhaps don't know the 
algorithms typically used in meta-analysis, there is a nice summary of 
the methods used in the revman package from the Cochrane collaboration:

Overall your question has the flavour of asking other people to just 
give you the answer without any work on your behalf. You would be 
advised to read the posting guide as recommended on the bottom of each 
R-help message, otherwise you might receive replies which appear to be 
quite offensive.

David Scott

David Scott	Department of Statistics
		The University of Auckland, PB 92019
		Auckland 1142,    NEW ZEALAND
Phone: +64 9 923 5055, or +64 9 373 7599 ext 85055
Email:	d.scott at auckland.ac.nz,  Fax: +64 9 373 7018

Director of Consulting, Department of Statistics

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