In R, how do you classify values ​​in one data frame based on ranges in another data frame?

Question

In general, how can I classify values ​​in one column of a data frame relative to factor values ​​in another data frame? For example, given df1 and df2, I would like to generate df3 (or update df1):

> df1 NewAge 1 5 2 25 3 18 4 9 5 43 6 15 7 17 > df2 AgeStart AgeEnd AgeType 1 0 10 A 2 10 20 B 3 20 30 A 4 30 40 B 5 40 50 A 

I want df3 as:

 NewAge Type 5 A 25 A 18 B 9 A 43 A 15 B 17 B 

I used cut () to generate intervals

 df2_cut <- data.frame(NewAge, "AgeRange" = cut(NewAge, breaks=AgeStart, right=F, include.lowest=T)) > df2_cut NewAge AgeRange 1 5 [0,10) 2 25 [20,30) 3 18 [10,20) 4 9 [0,10) 5 43 [40,50] 6 15 [10,20) 7 17 [10,20) 

but I don’t know how to classify df2_cut values ​​according to the type of interval (i.e. A or B).

Answer 1

We can use findInterval . The result will be a numerical index, which we use to get the corresponding elements from "AgeType".

 df3 <- transform(df1, Type=df2$AgeType[findInterval(NewAge, df2$AgeStart)]) df3 # NewAge Type #1 5 A #2 25 A #3 18 B #4 9 A #5 43 A #6 15 B #7 17 B 

Or with labels=FALSE in cut