The lazyeval package provides tools that make it easier to correctly implement non-standard evaluation (NSE) in R. You use lazy evaluation by requiring the user to "quote" specially evaluated arguments with ~, and then using the lazyeval package to compute with those formulas. It is also possible to eliminate the use of the ~ by converting promises to formulas. This does make programming with such functions a little harder, but it can be worth it in certain situations. See vignette("lazyeval") for more details.

Install the released version from CRAN with:

install.packages("lazyeval")

Install the development version from github with:

# install.packages("devtools")
devtools::install_github("hadley/lazyeval", build_vignettes = TRUE)

lazyeval is retired: this means only changes necessary to keep it on CRAN will be made. We recommend using rlang instead.