Replace values in data frame with other values according to a rule

Question

I am an beginner in R and don`t find a solution for the following problem. Any help would be really appreciated!

I have a data.frame and want to replace certain valu

Answer 1

You can use match:

dataframe <- transform(dataframe, Year = year[match(date, yearend)])

      date variable value Year
1 19921231        a     1 1992
2 19931231        a     2 1993
3 19941231        a     3 1994
4 19941231        b     4 1994
5 19931231        b     5 1993
6 19941231        b     6 1994