Hi,
I am a student using R for my final year project, with the metafor package
being particularly helpful. I have been following the steps laid out in the
manual 'Conducting Meta-analysis in R with the Metafor package' (Viechtbauer,
2010) and applying it to my own data of infected Anopheles mosquitoes across
Africa.
In particular, I am attempting to apply a mixed-effect model to my data with
absolute latitude as a moderator as per the example in the manual. I am able to
generate a plot of Relative Risk against absolute latitude without issue, but
when I try to add lines in from the predicted values generated I continually
get an error:
Error in xy.coords(x, y) : 'x' and 'y' lengths differ
However, I have used the length function on both my x and y co-ordinates and
found no difference in lengths. If anyone could shed some light on this I'd
really appreciate it. The code I used can be found below:
> mixed<-read.delim("regressiontest.txt")
> mixed
study year ablat mosq1pos mosq1neg mosq2pos mosq2neg
1 Cano et al. 2006 2 42 237 148 629
2 Kerah - Hinzoumbe et al. 2009 10 103 7260 3 215
3 Konate et al. 1994 13 83 5714 48 3609
4 Mwanzia et al. 2011 4 2 8971 0 100
> dat<-escalc(measure="RR", ai = mosq1pos, bi = mosq1neg, ci = mosq2pos, di =
> mosq2neg, data = mixed, append = TRUE)
> res<-rma(yi, vi, mods = ablat, data=dat)
> predict(res,transf = exp, addx = TRUE)
> preds<-predict(res, transf = exp)
> wi<-1/sqrt(dat$vi)
> size<-0.5 + 3 *(wi-min(wi))/(max(wi)) - min(wi)
> plot(dat$ablat, exp(dat$yi), pch = 19, cex = size, xlab = "Absolute
> Latitude", ylab = "Relative Risk", las=1, bty = "l", log = "y")
> lines(0:15, preds$pred)
Many thanks,
Charlotte Hewitt
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