# [R-meta] metafor forest 'ylim()': 1.row distances change, 2 .relative lines?

P. Roberto Bakker robertob@kker @ending from gm@il@com
Mon Sep 24 08:50:45 CEST 2018

```Hi Wolfgang,

My apologies, I did something wrong with registering. Now it should be
okay.

Thank you for your explaination. Very clear.

Still the study row distances change when the number of studies change (see
A next to B here below).
The journal asks for same distances.
As my meta-analyses are for different medication groups (each with
different number of studies) the study row distances vary between
meta-analyses.
So, what could I do?
Thank you in advance,
Roberto
###########A###############
yi <- c(.1, .3, .2, .5)
vi <- rep(.01, 4)
res <- rma(yi, vi)
forest(res)

### default for ylim is -1.5 to k+3
### summary polygon in y=-1
### line in y=0
### studies in y=1 to k
### line in y=k+1
forest(res, ylim=c(-1.5,res\$k+3))
text(0, -1:7, -1:7)

############B###############
yi <- c(.1, .3, .2, .5, .6, .5, .4)
vi <- rep(.01, 7)
res <- rma(yi, vi)
forest(res)

### default for ylim is -1.5 to k+3
### summary polygon in y=-1
### line in y=0
### studies in y=1 to k
### line in y=k+1
forest(res, ylim=c(-1.5,4))
text(0, -1:7, -1:20)
###########################

Op zo 23 sep. 2018 om 19:28 schreef Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl>:

> Maybe this helps -- go through this line by line.
>
> yi <- c(.1, .3, .2, .5)
> vi <- rep(.01, 4)
> res <- rma(yi, vi)
> forest(res)
>
> ### default for ylim is -1.5 to k+3
> ### summary polygon in y=-1
> ### line in y=0
> ### studies in y=1 to k
> ### line in y=k+1
> forest(res, ylim=c(-1.5,res\$k+3))
> text(0, -1:7, -1:7)
>
> ### change ylim
> forest(res, ylim=c(-3,10))
> text(0, -3:10, -3:10)
>
> ### this creates more space which we indicate subgroups and/or to add
> extra summary polygons
> forest(res, ylim=c(-3,10), row=c(6,5,2,1))
> text(0, -3:10, -3:10)
> text(par()\$usr, 7, "Group A", font=2, pos=4)
> text(par()\$usr, 3, "Group B", font=2, pos=4)
> addpoly(rma(yi, vi, subset=1:2), row=-2, mlab="Group A")
> addpoly(rma(yi, vi, subset=3:4), row=-3, mlab="Group A")
>
> Best,
> Wolfgang
>
> -----Original Message-----
> From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org] On Behalf Of P. Roberto Bakker
> Sent: Sunday, 23 September, 2018 12:01
> To: r-sig-meta-analysis using r-project.org
> Subject: [R-meta] metafor forest 'ylim()': 1.row distances change, 2
> .relative lines?
>
> Hi
>
> When I change 'ylim()', two things happen that I do not understand:
>
> 1) The study row distances change:
> - e.g. When I change from 'ylim=c(-1, 23)' into 'ylim=c(-1, 10)',  then
> 'y=c(-1, 5)', etc
> -> the study row distances increase at every step
> This whould not be a problem if I had only one forest plot - but I have
> several forest plots - so between forestplots the study row distances are
> different.
> 'rows=c()' could be a solution, however, the study row distances between
> forestplots still may differ.
>
> 2. The position of both horizontal lines change when I change one.
> e.g. at every step shown aboven the lower line changes position - the
> summary polygon may even disappear
>
> All in all, I seems to me that 'ylim()' zooms in/out at every change.
>
> In short: when I change one thing 'all other things change'.
>
> I hope I am clear.
>
> Syntax:
> forest(res, slab = paste(datsub\$npd, datsub\$tn, sep = ", "),
>          cex =0.45, cex.lab=0.8, cex.main=0.8, main="MAOI vs placebo - REML
> - R=0.5",
>          showweights = TRUE, order=order(datsub\$name),
>          ylim=c(-1,23))
>
> On my laptop: surface pro 4 64b
> R version 3.5.0 (2018-04-23) -- "Joy in Playing"
> Copyright (C) 2018 The R Foundation for Statistical Computing
> Platform: x86_64-w64-mingw32/x64 (64-bit)
>

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