Annotating ggplots inside a loop geom_hline is wrong

Question

I am trying to print a pdf with multiple plots. I am using a loop and ggplot, also this is inside a function. I am having trouble with 'annotating' the plot. I want to annotate the median for that condition, and the overall median. I am using a horizontal line (geom_hline) and annotate ('text') to label these lines.

The problem is that the words are being placed correctly (ie. annotate("text", x = 1, y = Cmedian) seems to work correctly, but the horizontal line is being drawn at the wrong location (ie. geom_hline(aes(yintercept=Cmedian) doesn't work,. It is always placing the Cmedian line at 30 and the allmedian line at 22.

I sometimes have 'strange' behaviours with ggplot inside a loop or a function and am wondering how to avoid this.

Any help is appreciated. Thank you,

suspect_conds<-c(head(suspect_SumPheno[rev(order(suspect_SumPheno$zscore)),],n=20)$condition,tail(suspect_SumPheno[rev(order(suspect_SumPheno$zscore)),],n=20)$condition)

pdf(paste(out_dir,paste(set,org,"bar.SuspectConditionssumPhenoPerPlate.pdf",sep="."),sep=""))
for (i in 1:length(suspect_conds)){
    cond<-suspect_conds[i]
    cond_subset<-PhenoSumPerPlatPerCond[PhenoSumPerPlatPerCond$condition==cond,]

    Cmedian<-median(cond_subset$sum_pheno)
    allmedian<-median(PhenoSumPerPlatPerCond$sum_pheno)
    plateMedians<-aggregate(sum_pheno~plate,data=PhenoSumPerPlatPerCond,median)  

    p<-ggplot(cond_subset, aes(x=plate, y=sum_pheno, fill=plate)) + geom_bar(stat="identity") + 
        labs(title=paste("total phenotypes per plate in",cond,sep=" ")) +   
        geom_hline(aes(yintercept=Cmedian), colour="black")+ geom_hline(aes(yintercept=allmedian), colour="black",linetype="dashed")+
        annotate("text", x = 1, y = Cmedian, label = "median number of phenotypes per plate in this condition",hjust=0,vjust=0)+ 
        annotate("text", x = 1, y = allmedian, label = "median number of phenotypes per plate",hjust=0,vjust=0)+
        geom_point(data=plateMedians,aes(x=plate,y=sum_pheno),colour="black",size=4)+
        theme_bw()

print(p,file=paste(out_dir,paste(set,org,cond,"bar.sumPhenoPerPlate.pdf",sep="."),sep=""))
}   
dev.off()

Puki Luki Puki Luki · Accepted Answer · 2015-05-07T11:32:34

I believe this problem is related to List for Multiple Plots from Loop (ggplot2). So as mentioned there, the only thing you need to do is replace aes(...) with aes_string(...).

Annotating ggplots inside a loop geom_hline is wrong

1 Answers