CODEWITHSUNDEEP
rdataframe
user2543427
user2543427

Reputation: 133

Divide a Column based on two Data Frames in R

Suppose I have two data frames, df and df2, that look like:

df

        User    Lab    Score
         A      1021    12
         A      1022    10
         A      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 to divide the Score column in df by the Score column in df2, depending on the Lab. Therefore I want to end up with a data frame that looks like:

        User    Lab    Score
        A       1021   0.8
        A       1022   1.0
        A       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

Upvotes: 0

Views: 1236

Answers (1)

Simon O'Hanlon
Simon O'Hanlon

Reputation: 59970

Just match the Labs up like this:

df$Score <- df$Score / df2$Score[ match( df$Lab , df2$Lab ) ]
#  User  Lab     Score
#1    A 1021 0.8000000
#2    A 1022 1.0000000
#3    A 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 the index of the first match of it's first argument in it's second argument. In English it returns which row in df2 is the match for each Lab in df.

Upvotes: 1

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