Subset and recombine dataframes using data.table package or other solutions [R]

Question

I am quite new to R and have a question about subset and recombine between two dataframe using range value of one of the variable. So i have my two dataframes like this :

Answer 1

This isn't possible in data.table nicely. It's FR#203 to implement. You could try package xts as I think that has this operation.

One long and clunky way (untested) in data.table is as follows. Say your first table is P and the 2nd table containing the ranges is R.

setkey(P,x)
# sort by x and mark as sorted so future queries can use binary search on P

from = P[J(R$min_x),which=TRUE]
# Lookup each min_x in the key of P, returning the location. J stands for Join.

to = P[J(R$max_x),which=TRUE]
# Lookup each max_x in the key of P, returning the location.

len = to-from+1
# vectorized for each item the length to[i]-from[i]+1

i = unlist(mapply("seq.int",from,to,SIMPLIFY=FALSE))
# for each item the sequence from[i]:to[i], then concat them all into one vector

cbind(rep(R$id,len), P[i])
# use len to expand the items of R to match what they match to in P