Creating a data frame of missing values

Question

I am working with petroleum company financial data and exploration data in RStudio

I have two data frames, AS and xpl.

When merging the two with merged = xpl %>% inner_join(AS, by=c("NPD_id", "year")), I lose some 90 observations from xpl.

Is there an easy way to create a new data frame from these missing 90 observations? A command which tells R to look for observations found in xpl, but not merged, and disregard the observations which are present in both frames maybe?

Thanks.