[R] editing plot

[Ana Marija]

Hello,

I have this plot in attach. I was wondering how can I change my
plotting code in order to remove these gray horizontal background
lines but keep these two vertical lines? These two vertical lines
don't need to be gray, can be any other type of lines but they must be
at the same place. Also how can I make these two bars narrower?

library("ggplot2")
p<-ggplot(data=toplot, aes(x=cat, y=props)) +
  geom_bar(stat="identity", fill="steelblue")+
  geom_errorbar(aes(ymin=props-1.96*ses, ymax=props+1.96*ses), width=.2,
                position=position_dodge(.9))  +

  geom_signif(comparisons=list( c("All eQTL", "eQTL from 103 genes"),
                               c("All SNPs", "eQTL from 103 genes")),
              y_position=c(0.065, 0.07), tip_length=0, annotation=c("p
= 0.0012", "p = 0.0023")) +
  scale_y_continuous(breaks=seq(0,.06,by=.01)) +
  xlab("") + ylab("Proportion p-values < 0.05") +
  theme_minimal()
p

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