通过R中另一个数据框的值的唯一组合来子集一个数据框

Question

I have a large dataframe A similar to the following and a second one, B, containing only lat/lon values. What I am trying to do is to subset dataframe A based on the unique combinations of lat/lon from dataframe B. So far, I have tried the following but does not work. How should I change my code in order to effectively do this?

head(A)
  vals       time     lon  lat mo year
1        5 1978-11-01 100 32    01 1988
2        3 1978-11-02 100 45    02 1988
3        3 1978-11-03 100 45    01 1998
4        9 1978-11-04 100 50    05 1998
5        1 1978-11-05 100 60    05 1998
6        4 1978-11-06 100 32    05 1998



A_subset <-subset(A, A[, "lon"] %in% B$lon | A[, "lat"]
                 %in% B$lat)

Answer 1

Consider running an expand.grid on data frame B for all combination of unique coordinates. Then merge to data frame A:

B_all_combns <- expand.grid(lon = unique(B$lon), lat = unique(B$lat))

A_subset <- merge(A, B_all_combns, by=c("lon", "lat"))