Using one data.frame to update another

Question

Given 2 data frames that are identical in terms of column names/datatypes, where some columns uniquely identify the rows, is there an efficient function/method for one data.

Answer 1

require(plyr)
indexes_to_replace <- rownames(match_df(original,replacement,on='Id'))
indexes_from_replace<-rownames(match_df(replacement,original,on='Id'))
original[indexes_to_replace,] <- replacement[indexes_from_replace,]

param on of function match_df can take vectors as well.