r - dplyr - Aggregation incorrect? -

i have som issues dplyr , group_by function not working expected. using summarise, expect mean of var1 each unique combination of id , year entered group_by statement.

this code should create df id-year observations, want aggregate mean of var 1 each combination of id , year. however, not working expected , output ignores id, , aggregates on year.

df <- data.frame(id=c(1,1,2,2,2,3,3,4,4,5),                  year=c(2013,2013,2012,2013,2013,2013,2012,2012,2013,2013),                   var1=rnorm(10)) 

dplyr code:

dfagg <- df %.%   group_by(id, year) %.%   select(id, year, var1) %.%   summarise(     var1=mean(var1)     ) 

result:

> dfagg source: local data frame [8 x 2] groups: year    year        var1 1 2013  0.22924025 2 2012 -0.93073687 3 2013 -0.82351583 4 2012  0.05656113 5 2013 -0.21622021 6 2012  1.91158209 7 2013 -2.67003628 8 2013 -0.72662276 

any idea going on?

to make sure no other package interrupted dplyr functions tried below same result.

dfagg <- df %.%   dplyr::group_by(id, year) %.%   dplyr::select(id, year, var1) %.%   dplyr::summarise(     var1=mean(var1)     ) 

i don't think need select() line. using group_by() , summarise() did trick me.

library(dplyr)  df <- data.frame(id=c(1,1,2,2,2,3,3,4,4,5),                  year=c(2013,2013,2012,2013,2013,2013,2012,2012,2013,2013),                   var1=rnorm(10)) df %>%   group_by(id, year) %>%   summarise(mean_var1=mean(var1)) -> dfagg 

result:

     id  year   mean_var1   (dbl) (dbl)       (dbl) 1     1  2013 -1.20744511 2     2  2012 -0.59159641 3     2  2013 -0.03660552 4     3  2012 -0.38853566 5     3  2013 -1.76459495 6     4  2012 -0.66926387 7     4  2013  0.70451751 8     5  2013 -0.82762769