R example of dplyr's mutate and lag with magrittr to flexibly add lags to a data.frame

lag_gen

#
# Example of dplyr's mutate and lag with magrittr's %>%
# to flexibly add lags to a data.frame
#
library(dplyr)
library(magrittr) # >= v.1.0.1

# A function to generate a mutate call
lag_gen <- function(x, lags)
{
  x <- substitute(x)
  
  (function(l) substitute(lag(x, l), list(x = x, l = l))) %>%
    lapply(X = lags) %>%
    set_names(paste0(x, ".", lags)) %>%
    append(quote(mutate), after = 0) %>%
    as.call
}
    
# A test data set.
test_data <- 
  data.frame(
    id = rep(1:10, each = 8),
    t  = rep(1:8, 10),
    value = runif(80)
  )

# Try it out. Remember to put lag_gen in 
# parens as it is the resulting call we use.
test_data %>%
  group_by(id) %>%
  (lag_gen(value, c(1, 2, 7))) %>% 
  head(16)