dplyr left join only certain columns
df1 <- data.frame(id=1:3,day=2:4,element=3:5,value1=100:102)
df2 <- data.frame(id=1:3,day=3:5,element=4:6,value2=200:202)
df1
# id day element value1
#1 1 2 3 100
#2 2 3 4 101
#3 3 4 5 102
df2
# id day element value2
#1 1 3 4 200
#2 2 4 5 201
#3 3 5 6 202
left_join(df1, df2)
#Joining by: c("id", "day", "element")
# id day element value1 value2
#1 1 2 3 100 NA
#2 2 3 4 101 NA
#3 3 4 5 102 NA
left_join(df1, select(df2, c(id,value2)), by = "id")
# id day element value1 value2
#1 1 2 3 100 200
#2 2 3 4 101 201
#3 3 4 5 102 202