Inner Join with conditions in R

Question

I want to do inner join with the condition that it should give me subtraction of 2 columns.

df1 = data.frame(Term = c(\"T1\",\"T2\",\"T3\"), Sec = c(\         


        

Answer 1

As this is a dplyr question, here is a dplyr solution :

First use inner_join and then transmute to keep variables and compute and append a new one.

inner_join(df1, df2, by = "Sec") %>% 
  transmute(Term = Term.x, Sec, Value = abs(Value.x - Value.y))

Answer 2

Here is a "base R" solution using the merge() function on the Term column shared by your original df1 and df2 data frames:

df_merged <- merge(df1, df2, by="Sec")
df_merged$Value <- abs(df_merged$Value.x - df_merged$Value.y)
df_merged <- df_merged[, c("Sec", "Term.x", "Value")]
names(df_merged)[2] <- "Term"

> df_merged
  Sec Term Value
1  s1   T1    30
2  s2   T2    20
3  s3   T3    10

Answer 3

Using data.tables binary join you can modify columns while joining. nomatch = 0L makes sure that you are doing an inner join

library(data.table)
setkey(setDT(df2), Sec)
setkey(setDT(df1), Sec)[df2, .(Term, Sec, Value = abs(Value - i.Value)), nomatch = 0L]
#    Term Sec Value
# 1:   T1  s1    30
# 2:   T2  s2    20
# 3:   T3  s3    10