[R] Bar Plots: Error Bars

bshan101 bshan101 at gmail.com
Thu Dec 3 08:18:33 CET 2009


Hey Everyone,

I'm pretty new at R and wanted to try and make some graphs with dummy data
before using it to analyze my own. I successfully made a bar graph and error
bars, but I can't figure out how to align them properly (currently they are
not centered on the bars and some of them aren't even close). Here's the
code that I'm using:

> marks <- sample(4:10, size=50, replace=TRUE)
> dim(marks) <- c(10,5)
> classavg <- colMeans (marks, na.rm=FALSE, dims = 1) 
> barplot(classavg, main="Class Average for Quizzes", xlab="Quiz",
> ylab="Average", names = c("1","2","3","4","5"), ylim=c(0,12), axis.lty=1)
box()
> max <- apply (marks, 2, max)
> min <- apply (marks, 2, min)
> arrows(1:5, min, 1:5, max, code=3, angle=90, length=0.125)

The error bars are simply ranges for now (I wanted to do that before I tried
standard deviation/error). If anyone could help me align them it would be
much appreciated!

brett

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