dataframe - Divide a Column based on two Data Frames in R -

suppose have 2 data frames, df , df2, like:

df

        user    lab    score               1021    12               1022    10               1024    15          b      1021    9          b      1022    9          b      1023    14          c      1024    10 

df2

        lab    score         1021    15         1022    10         1023    15         1024    15 

i want divide score column in df score column in df2, depending on lab. therefore want end data frame looks like:

        user    lab    score               1021   0.8               1022   1.0               1024   1.0         b       1021   0.6         b       1022   0.9         b       1023   0.93         c       1024   0.67 

where 12/15 = 0.8, 10/10 = 1.0, 15/15 = 1.0,9/15 = 0.6, 9/10 = 0.9, 14/15 = 0.9333, 10/15 = 0.6667

just match labs this:

df$score <- df$score / df2$score[ match( df$lab , df2$lab ) ] #  user  lab     score #1    1021 0.8000000 #2    1022 1.0000000 #3    1024 1.0000000 #4    b 1021 0.6000000 #5    b 1022 0.9000000 #6    b 1023 0.9333333 #7    c 1024 0.6666667 

match returns index of first match of it's first argument in it's second argument. in english returns row in df2 match each lab in df.