Add row to data frame with dplyr

With tibble version 1.2 you can use add_row()

https://blog.rstudio.org/2016/08/29/tibble-1-2-0/

data %>% 
 add_row(cvar = "add", nvar1 = sum(nvar1), nvar2 = sum(nvar2))

Using only dplyr you could do the following

data %<>%
  summarise(cvar = "add",
            nvar1 = sum(nvar1),
            nvar2 = sum(nvar2)) %>%
  bind_rows(data)

which results in

        cvar nvar1 nvar2
1        add    27    18
2 2015-11-01    12     7
3 2015-11-02    10     5
4        All     5     6

Note that this way the new row is added at the beginning rather than the end of the original dataframe.

If you want to add the new row at the end instead, use the following code (thanks to krlmlr for pointing this out)

data %<>%
  summarise(cvar = "add",
            nvar1 = sum(nvar1),
            nvar2 = sum(nvar2)) %>%
  bind_rows(data, .)

which results in

        cvar nvar1 nvar2
1 2015-11-01    12     7
2 2015-11-02    10     5
3        All     5     6
4        add    27    18

One option utilizing summarise_all() and bind_rows() could be:

data %>% 
 bind_rows(summarise_all(., ~ if (is.numeric(.)) sum(.) else "add"))

        cvar nvar1 nvar2
1 2015-11-01    12     7
2 2015-11-02    10     5
3        All     5     6
4        add    27    18

Or adding the row and then calculating the sum only for that last row using if_else():

data %>%
 add_row(cvar = "add") %>%
 mutate_at(-1, ~ if_else(row_number() == max(row_number()), sum(., na.rm = TRUE), .))

Or an alternative to @Rickard's answer when the variables are not in global environment:

data %>% 
 add_row(cvar = "add", nvar1 = sum(data$nvar1), nvar2 = sum(data$nvar2))

Something like this then maybe:

data %>% 
     rbind(c("add",sum(nvar1),sum(nvar2)))
#        cvar nvar1 nvar2
#1 2015-11-01    12     7
#2 2015-11-02    10     5
#3        All     5     6
#4        add    27    18

Edit:

According to your comment, this will work:

data %>% 
  mutate(nvar3 = nvar1) %>% 
  rbind(c("add",sum(nvar1),sum(nvar2),sum(.$nvar3))) 

Using the . will allow rbind to find nvar3

Edit2:

Provide the new row as a list and it will maintain the column classes:

> str(
+ data %>% 
+   mutate(nvar3 = nvar1) %>% 
+   rbind(list("add",sum(nvar1),sum(nvar2),sum(.$nvar3))) 
+ )
'data.frame':   4 obs. of  4 variables:
 $ cvar : chr  "2015-11-01" "2015-11-02" "All" "add"
 $ nvar1: num  12 10 5 27
 $ nvar2: num  7 5 6 18
 $ nvar3: num  12 10 5 27