dotchartN<-function(x, y, err.bars="ci", pch=16, col=1,
                    length=0.05, las=2,
                    ylab=names(y), xlab = "Group", ...){
x<-as.factor(x)
par(mar=c(5,5,2,2))
means<-tapply(y, x, mean)
if (err.bars=="se") int<-sqrt(tapply(y, x, var)/(tapply(y, x, length)-1))
if (err.bars=="ci") {int<-sqrt(tapply(y, x, var)/(tapply(y, x, length)-1))*qt(0.975, tapply(y, x, length)-1)}
if (err.bars!="range") {
maxs<-means+int
mins<-means-int
}
if (err.bars=="range") {
maxs<-tapply(y, x, max)
mins<-tapply(y, x, min)
}
ymi<-min(mins)
yma<-max(maxs)
ymi<-ymi-0.1*(yma-ymi)
yma<-yma+0.1*(yma-ymi)


plot(1:length(levels(x)), means,
     ylim=c(ymi, yma),
     xlim=c(0.5, length(levels(x))+0.5), las=las,
     xaxt='n', pch=pch, col=col, ylab=ylab, xlab=xlab)
axis(1, 1:length(levels(x)), labels=levels(x))
arrows(1:length(levels(x)), y0=mins, y1=maxs, code=3, angle=90,
       length = 0.05, col=col)
}