tdid-example • tdid

How to run TDID

Load the library

library(tdid)
library(ggplot2)

Upload data

data = tdid::example_dgp(1000)
head(data)
#>   id time group W         X           Y
#> 1  1    1     A 1 2.0291407  1.34347905
#> 2  2    1     A 1 1.9147749  1.12206040
#> 3  3    1     A 0 0.9975437  0.59053958
#> 4  4    1     A 1 1.1360096 -0.01266106
#> 5  5    1     B 0 2.2049405  3.32070095
#> 6  6    1     B 0 3.3404646  2.46100783

Estimate TDID with controls

tdid::drtdid(data)
#>        tau    tau.se     dr_A     dr_B      wdr
#> 1 3.493839 0.5759991 5.212504 6.196596 1.718665

Replicate the graph from the paper

Single iteration

single_it = function(n, seed) {
  data = example_dgp(n = n, seed = seed)
  mod = drtdid(data)
  return(mod)
}

Monte Carlo simulations

reps = 2000
N = 2000
res = parallel::mclapply(1:reps, single_it, n = N) |> dplyr::bind_rows()

Plot results

res |> 
  dplyr::mutate(diff_dr = dr_A - dr_B) |> 
  ggplot() + 
  geom_density(aes(x = tau, fill = "DR A - WDR B"), alpha = .5) +
  geom_density(aes(x = diff_dr, fill = "DR A - DR B"), alpha = .5) +
  geom_vline(aes(xintercept = mean(res$dr_A - res$dr_B), color = "DR A - DR B"), linetype = "dashed", size = 1) +
  geom_vline(aes(xintercept = mean(res$tau), color = "DR A - WDR B"), linetype = "dashed", size = 1) +
  scale_x_continuous(breaks = -3:5, limits = c(-3, 5)) +
  guides(color = "none") + 
  theme(legend.position = "bottom") + 
  labs(x = "Estimated Difference", y = "Density", fill = NULL)
#> Warning: Using `size` aesthetic for lines was deprecated in ggplot2 3.4.0.
#> ℹ Please use `linewidth` instead.
#> This warning is displayed once every 8 hours.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.
#> Warning: Removed 1 row containing non-finite outside the scale range
#> (`stat_density()`).
#> Warning: Removed 6 rows containing non-finite outside the scale range
#> (`stat_density()`).