Hello,
If I understand it right, you can use the arrows() function with an
angle of 90 to get ci bars.
Using your data example, but with made up standard errors,
a=c(10,15)
b=c(20,24)
c=c(21,23)
hei=cbind(a,b,c)
# Standard errors
sigma <- matrix(runif(6), ncol = 3)
# helper function
ci <- function(x, conf = 0.95) x*qnorm(1 - (1 - conf)/2)
lo <- hei - ci(sigma)
hi <- hei + ci(sigma)
graph1=barplot(hei, beside=T, ylim = c(0, max(hi)))
sapply(1:ncol(graph1), function(j){
arrows(graph1[,j], hei[,j], graph1[,j], lo[,j], length = 0.15,
angle = 90)
arrows(graph1[,j], hei[,j], graph1[,j], hi[,j], length = 0.15,
angle = 90)
})
Hope this helps,
Rui Barradas
Em 08-11-2012 13:02, Thais Rangel escreveu:
Hello everyone!
I need to include the confidence interval bar in a grouped barplot. I've
found some options on the web, but none of them solved my problem.
The question is: my barplot was created using vectors for each pair of bar
and them combining them using cbind.
I mean:
a=c(10,15)
b=c(20,24)
c=c(21,23) ...
hei=cbind(a,b,c)
graph1=barplot(hei, beside=T,...)
I've tried to include each CI in a vector just like the height of the bars,
but it hasn't worked (!!)
Is there an easy way to do this??
Thanks a lot =)
Thais Rangel
(Rio de Janeiro, Brazil)
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