how to use merge() to update a table in R

Question

I\'m trying to figure out how to use merge() to update a database.

Here is an example. Take for example the data frame foo

Answer 1

Another approach could be:

1. Remove the NAs from the first data fram

2. Use rbind to append the data instead of using merge:

These are the original two data frames:

foo <- data.frame(index=c('a', 'b', 'c', 'd'), value=c(100, 101, NA, NA))
bar <- data.frame(index=c('c', 'd'), value=c(200, 201))

(1) Use the negation of is.na to remove the NAs:

foo_new <- foo[!is.na(foo$value),]

(2) Bind the data frames and you'll get the answer you were looking for

new_df <- rbind(foo_new,bar)

            new_df
            index value
            1     a   100
            2     b   101
            3     c   200
            4     d   201