A simple example showing how to add error bars to a bar plot.

barplot with error bars example.R

#bar heights
x<- c(1,2,3,2,4)

#standard error values
sem <- c(.5,.4,.2,.4,.2)

#bar labels

lab <- c("A","B","C","D","E")

#basic plot
d<-barplot(x,names.arg = lab,ylim=c(0,5))

#adding error bars
arrows(x0 = d,y0 = (x-sem),x1 = d,y1 = (x+sem),code = 3,length=0.1,angle=90)