show observation that got lost in merge

Question

Lets say I want to merge two different dataframes by the key of two columns.

Dataframe One has 70000 obs of 10 variables. Dataframe Two has 4500 obs of 5 variables.

Answer 1

I think you can use dplyr::anti_join for this. From its documentation:

return all rows from x where there are not matching values in y, keeping just columns from x.

You'd probably have to pass your data frame TWO as x.

EDIT: as mentioned in the comments, the syntax for its by argument is different.

Example:

df1 <- data.frame(Name=c("a", "b", "c"),
                  Date1=c(1,2,3),
                  stringsAsFactors=FALSE)

df2 <- data.frame(Name=c("a", "d"),
                  Date2=c(1,2),
                  stringsAsFactors=FALSE)

> dplyr::anti_join(df2, df1, by=c("Name"="Name", "Date2"="Date1"))
  Name Date
1    d    2