dan - 1 year ago 86
R Question

# Scaling the base line of geom_bar

I'm trying to generate a bar plot using

`geom_bar`
. My bars have both negative and positive values:

``````set.seed(1)
df <- data.frame(y=log(c(runif(6,0,1),runif(6,1,10))),se=runif(12,0.05,0.1),name=factor(rep(c("a","a","b","b","c","c"),2),levels=c("a","b","c")),side=factor(rep(1:2,6),levels=1:2),group=factor(c(rep("x",6),rep("y",6)),levels=c("x","y")),stringsAsFactors=F)
``````

This plot command plots the positive bars to face up and the negative ones to face down:

``````library(ggplot2)
dodge <- position_dodge(width=0.9)
limits <- aes(ymax=y+se,ymin=y-se)
ggplot(df,aes(x=name,y=y,group=interaction(side,name),col=group,fill=group))+facet_wrap(~group)+geom_bar(width=0.6,position=position_dodge(width=1),stat="identity")+
geom_bar(position=dodge,stat="identity")+geom_errorbar(limits,position=dodge,width=0.25)
``````

My question is how do I set the base line to the minimum of all bars instead of at 0 and therefre have the red bars facing up?

This simple hack also works:

``````m <- min(df\$y) # find min
df\$y <- df\$y - m
ggplot(df,aes(x=name,y=y,group=interaction(side,name),col=group,fill=group))+
facet_wrap(~group)+
geom_bar(width=0.6,position=position_dodge(width=1),stat="identity")+
geom_bar(position=dodge,stat="identity")+
geom_errorbar(limits,position=dodge,width=0.25) +
scale_y_continuous(breaks=seq(min(df\$y), max(df\$y), length=5),labels=as.character(round(seq(m, max(df\$y+m), length=5),2))) # relabel
``````

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