An R package for computing the standardized mean difference between two groups for various data types.

library(smd)

x <- rnorm(100)
g <- rep(1:2, each = 50)

smd(x, g, std.error = TRUE)
#>   term  estimate std.error
#> 1    2 0.1653336 0.2003414

See using smd for more details.