Is there a way to create Stata's _merge indicator variable with R's merge()?

Question

Stata automatically creates a variable called \"_merge\" indicating the matched variables in both datasets after merge. Is there a way to get such variable generated by R\'s

Answer 1

The possible values of _merge in Stata are (note merge can also have values 4 and 5)

              1       master             observation appeared in master only
              2       using              observation appeared in using only
              3       match              observation appeared in both

In R, you can do that by entering the argument as either all=TRUE or all.x=TRUE or all.y=TRUE

e.g.,

merge(x, y, by = intersect(names(x), names(y)),by.x = by, by.y = by, all = TRUE)
 merge(x, y, by = intersect(names(x), names(y)),by.x = by, by.y = by, all.x = TRUE)
 merge(x, y, by = intersect(names(x), names(y)),by.x = by, by.y = by, all.y = TRUE)