Merge dataframes in R with different size and condition

Question

I\'m trying to combine 2 csv files into one file. They have common id with different size. I used merge() but I got replicated data. I have the following data-frames;

Answer 1

An option is regex_left_join from fuzzyjoin

library(fuzzyjoin)
library(dplyr)
regex_left_join(data2, data1, by = c("SR", "class" = "school")) %>%
      select(SR = SR.x, school, class, Y)

#    SR    school   class    Y
# 1  SR1    S-1     S-1.2    3
# 2  SR1    S-1     S-1.5    3
# 3  SR1    S-1     S-1.7    3
# 4  SR2    S-1     S-1.1    4
# 5  SR2    S-1     S-1.2    4
# 6  SR2    S-1     S-1.3    4
# 7  SR2    S-1     S-1.6    4
# 8  SR2    S-2     S-2.3    1
# 9  SR2    S-2     S-2.9    1
# 10 SR2    S-4     S-4.2    2
# 11 SR3    S-2     S-2.1    5
# 12 SR3    S-2     S-2.3    5
# 13 SR4    S-1     S-1.5    2
# 14 SR4    S-1     S-1.6    2
# 15 SR4    S-5     S-5.1    3