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

merge() might also be of help.

yearend<-c("19921231","19931231","19941231")
year<-c("1992","1993","1994")
map = data.frame(yearend,year)

merge(dataframe,map,by.x='date',by.y='yearend')