Question

How can I achieve a cross join in R ? I know that “merge” can do inner join, outer join. But I do not know how to achieve a cross join in R.

Thanks

Answer 1

Is it just all=TRUE?

x<-data.frame(id1=c("a","b","c"),vals1=1:3)
y<-data.frame(id2=c("d","e","f"),vals2=4:6)
merge(x,y,all=TRUE)

From documentation of merge:

If by or both by.x and by.y are of length 0 (a length zero vector or NULL), the result, r, is the Cartesian product of x and y, i.e., dim(r) = c(nrow(x)*nrow(y), ncol(x) + ncol(y)).