Creating A New Calculated Category Within A Column in R

Suppose I have a data frame similar to this, only with 1000’s of observations:

df <- data.frame(Group = c('A', 'A', 'A', 'B', 'B',
                           'B','B','C','C','C','D','D','D','D','D'),
                 Values=c('5','7','9','0','8','4','5','2','1','3','6','3','1','3','5'))

What I want to do is add a new calculated group to the data frame based on values in a group that already exists in the data frame without replacing the original group’s values. For example, lets say I want to retain group D, but create a new group with all of group D’s values +2.

An example of the resulting dataframe I would like is the following:

df <- data.frame(Group = c('A', 'A', 'A', 'B', 'B',
                           'B','B','C','C','C','D','D','D','D','D'
                           ,'Dadjusted','Dadjusted','Dadjusted','Dadjusted','Dadjusted'),
                 Values=c('5','7','9','0','8','4','5','2','1','3','6','3','1','3','5',
                          '8','5','3','5','7'))

I have tried using ifelse statements like the following:

   df$adjustedvalues<-ifelse(Group=='D', df$Values+2, df$Values)

but this approach results in data frames that look like the following:

df <- data.frame(Group = c('A', 'A', 'A', 'B', 'B',
                           'B','B','C','C','C','D','D','D','D','D'),
                 Values=c('5','7','9','0','8','4','5','2','1','3','6','3','1','3','5')
                 adjustedvalues=c('5','7','9','0','8','4','5','2','1','3','8','5','3','5','7')

Which is less than ideal for my purposes.

>Solution :

Here is a possible base R option:

rbind(df, data.frame(Group = "Dadjusted", 
                     Values = as.integer(df$Values)[df$Group == "D"]+2))

Output

       Group Values
1          A      5
2          A      7
3          A      9
4          B      0
5          B      8
6          B      4
7          B      5
8          C      2
9          C      1
10         C      3
11         D      6
12         D      3
13         D      1
14         D      3
15         D      5
16 Dadjusted      8
17 Dadjusted      5
18 Dadjusted      3
19 Dadjusted      5
20 Dadjusted      7

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