mtcars %>% 
  lazy_dt() %>% 
  transmute(hp = 1, mpg = 2)
#> Source: local data table [1 x 2]
#> Call:   `_DT4`[, .(hp = 1, mpg = 2)]
#> 
#>      hp   mpg
#>   <dbl> <dbl>
#> 1     1     2
#> 
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results

mtcars %>% 
  lazy_dt() %>% 
  mutate(hp = 1, mpg = 2, .keep = 'none')
#> Source: local data table [32 x 2]
#> Call:   copy(`_DT5`)[, `:=`(hp = 1, mpg = 2)][, `:=`(c("cyl", "disp", 
#> "drat", "wt", "qsec", "vs", "am", "gear", "carb"), NULL)]
#> 
#>      mpg    hp
#>    <dbl> <dbl>
#>  1     2     1
#>  2     2     1
#>  3     2     1
#>  4     2     1
#>  5     2     1
#>  6     2     1
#>  7     2     1
#>  8     2     1
#>  9     2     1
#> 10     2     1
#> # ℹ 22 more rows
#> 
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results

pacman::p_load(dtplyr, dplyr)

data <- data.frame(x = c("A", "A", "B", "B"), y = c(1, 2, 3, 4))

lazy_dt(data) %>%
  transmute(mean_y = mean(y))
#> Source: local data table [1 x 1]
#> Call:   `_DT1`[, .(mean_y = mean(y))]
#> 
#>   mean_y
#>    <dbl>
#> 1    2.5
#> 
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results