r - Check if each row of a data frame is contained in another data frame

Question

I wrote the following function, it works. However it is very slow when df1 has 1700 rows, and df2 has 70000 rows. Is there anyway to improve the efficiency?

rowcheck <- function(df1, df2){
         apply(df1, 1, function(x) any(apply(df2, 1, function(y) all(y==x))))
}

An example I wrote this function to apply to is: I want to check whether each row in df1 is contained as a row in df2:

df1=data.frame(a=c(1:3),b=c("a","b","c"))
df2=data.frame(a=c(1:6),b=rep(c("a","b","c"),2))

For each row of df1, I want to check if it is contained as a row in df2. I want to return of the function to be a logical vector of length nrow(df1).

Thank you for your help.

Answer 1

One way is to paste the rows together, and compare them with %in%. The result is a logical vector the length of nrow(df1), as requested.

do.call(paste0, df1) %in% do.call(paste0, df2)
# [1] TRUE TRUE TRUE