[R] Summarising Data for Forrest Plots

[Viechtbauer Wolfgang (STAT)]

Are n.FD and n.RD the number of people who received the full/reduced dose and surv.FD and surv.RD the number of people that survived? And are the people who received the full dose different from the people who received the reduced dose? And what exactly is it that you want to plot in the forest plot? From the way you have arranged the table, it seems as if you want some kind of effect size measure that contrasts the survival rate of the full versus reduced dose in the various subgroups. Is that correct? And are you just trying to figure out how to draw the forest plot once you have the data in the table form as shown in your post or are you also trying to figure out how to create that table to begin with?

--
Wolfgang Viechtbauer
 Department of Methodology and Statistics
 University of Maastricht, The Netherlands
 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 Polwart Calum
(County Durham and Darlington NHS Foundation Trust) Sent: Tuesday, July
28, 2009 20:28 To: r-help at r-project.org Subject: [R] Summarising Data
for Forrest Plots

> I tried to post this a few times last week and it seems to have got
> stuck somehow so I'm trying from a different email in the hope that
> works.   If somehow this has appeared on the list 20 tiems and I
> never saw any of them I apologize ;-)
>
> I'm basically an R-newbie.  But I am VERY computer literate.  But
> this has me stumped...
>
> All the examples for using the rmeta package to create a forest plot
> or simillar seem to use the catheter data:
>
>          Name n.trt n.ctrl col.trt col.ctrl inf.trt inf.ctrl
> 1      Ciresi   124    127      15       21      13       14
> 2      George    44     35      10       25       1        3
> 3      Hannan    68     60      22       22       5        7
> 4       Heard   151    157      60       82       5        6
> ...
>
> As I see it thats a summary of data from several published trials.
>
> What I want to do is do a forrest (forest) plot for subgroups within
> my single dataset as a test of heterogeniety. I have a dataset who
> received either full dose(FD) or reduced dose(RD) treatment, and a
> number of characteristics about those subjects: age, sex, renal
> function, weight, toxicity.  And I have survival data (censored).
> they are in standard columnar data.
>
> Is there an *easy* way to transform them into something like this:
>
>         SubGroup        n.FD    n.RD    surv.FD         surv.RD
> 1       Age >65
> 2       Age <= 65
> 3       Male
> ...
> 9       Grade 0-2 Tox
> 10      Grade 3/4 Tox
>
> Which rmeta will then let me use to create a forest plot from?  This
> is a reasonably standard approach in biomedical studies these days so
> it seems odd that I can't find any "How-To" that tells me how to
> short cut it.  Otherwise I have to manually calculate each of the
> parameters :-(  Which is a real pain as we are awaiting more mature
> data which would need the same process re-run.
>
> Thanks in advance
>
> C
>
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