subtotals by group R

I'm trying to find a function similar to SAS's Proc Means which will aggregate data and subtotal/total it by groups.

For example I have:

Var1    Var2
 a       b  
 a       c  
 b       b

and I want to create:

Var1    Var2    N
 a       b      1
 a       c      1
 b       b      1
 na      b      2
 na      c      1
 a       na     2
 b       na     1
 na      na     3

I've found that Summarise() and Aggregate() are able to do this but without the subtotals. There is also a Cube() function in development for data.table which does this, but I can only download from CRAN due to our IT security policy.

As you can probably tell, I'm new to R so I'm sorry if this is a fairly simple question.

Thanks!

Solution

Using DF in the Note at the end try this one-liner. The same code works if there are a different number of columns. Also try it without the as.data.frame for wide format. No packages are used.

as.data.frame(addmargins(xtabs(~., DF)))

giving:

  Var1 Var2 Freq
1    a    b    1
2    b    b    1
3  Sum    b    2
4    a    c    1
5    b    c    0
6  Sum    c    1
7    a  Sum    2
8    b  Sum    1
9  Sum  Sum    3

Note

DF in reproducible form is:

DF <- structure(list(Var1 = structure(c(1L, 1L, 2L), .Label = c("a", 
"b"), class = "factor"), Var2 = structure(c(1L, 2L, 1L), .Label = c("b", 
"c"), class = "factor")), class = "data.frame", row.names = c(NA, 
-3L))