Binding dataframes by multiple conditions in R -

i have data frame looks this:

> data   class number 1          1 2          2 3          3 4     b      1 5     b      2 6     b      3 7     c      1 8     c      2 9     c      3 

i have reference data frame is:

> reference   class number value 1          1   0.5 2     b      3   0.3 

i want join these data frames create single data frame:

> resultdata   class number value 1          1   0.5 2          2   0.0 3          3   0.0 4     b      1   0.0 5     b      2   0.0 6     b      3   0.3 7     c      1   0.0 8     c      2   0.0 9     c      3   0.0 

how can achieve this? appreciated

you can do

library(data.table) setkey(setdt(reference), class, number)[data] 

or

setkey(setdt(data), class, number)[reference,                value:= i.value][is.na(value), value:=0] #    class number value #1:          1   0.5 #2:          2   0.0 #3:          3   0.0 #4:     b      1   0.0 #5:     b      2   0.0 #6:     b      3   0.3 #7:     c      1   0.0 #8:     c      2   0.0 #9:     c      3   0.0