R: How do I split a variable into named intervals? - r

Question

I am working on a rather large dataset in R, containing a continuous numeric variable. In another dataset, I have named intervals, described by min and max values, that I want to apply to the continuous variable in my large dataset.
Below is some example code:
df<-data.frame(x=c(1:6))
groups<-data.frame(cat=c("a","b","c","d"), min=c(1,2,4,6), max=c(2,4,5,8))
I want to make a new column, df$cat, so that the values of df$x are within the min-max boudaries found in the groups data frame.
Ideally, I would like to have groups$min >= df$x > groups$max.
> df
x cat
1 1 a
2 2 b
3 3 b
4 4 c
5 5 d
6 6 d
Is there any easy way of doing this?

Answer 1

Set up data:
df <- data.frame(x=c(1:6))
groups <- data.frame(cat=c("a","b","c","d"), min=c(1,2,4,6), max=c(2,4,5,8))
Use cut() with the labels argument specified:
brks <- c(groups$min,tail(groups$max,1))
df$cat <- cut(df$x,breaks=brks,labels=groups$cat,right=FALSE)

Answer 2

df<-data.frame(x=c(1:6))
groups<-data.frame(cat=c("a","b","c","d"), min=c(1,2,4,6), max=c(2,4,5,8))
for(i in 1:nrow(groups)){
numbers_in_range = df$x[df$x >= groups[i,]$min & df$x <= groups[i,]$max]
df[,i+1] = df$x %in% numbers_in_range
colnames(df)[2:ncol(df)] = as.character(groups$cat)
}
something like this will tell you which numbers are in which groups ranges. Is this what you were after?