Question

I'm trying to figure out a formula to be able to divide the max and min number inside the intervals.

Answer 1

#One possible solution is to split by (,] (xout is your dataframe)

x1<-strsplit(as.character(xout$factorx),",|\\(|]")
x2<-do.call(rbind,x1)
xout$lower=as.numeric(x2[,2])
xout$higher=as.numeric(x2[,3])
xout$ave<-rowMeans(xout[,c("lower","higher")])

> head(xout,3)
      factorx Freq cumFreq relative higher lower   aver
1 (9.97,13.7]   15      15     0.15   13.7  9.97 11.835
2 (13.7,17.5]   14      29     0.14   17.5 13.70 15.600
3 (17.5,21.2]   12      41     0.12   21.2 17.50 19.350