Kolmogorov–Smirnov tests with non-standard evaluation

ks_test.R

library(rlang)
library(dplyr)

# ----------------------------------------------------------------
# First implementation: specify desired variable names explicitly.
# ----------------------------------------------------------------

test1 <- function(var1, var2, data, name1, name2) {
  qvar1 <- enquo(var1)
  qvar2 <- enquo(var2)
  assign(name1, pull(data, !!qvar1))
  assign(name2, pull(data, !!qvar2))
  substitute(
    expr = ks.test(x, y),
    env = list(x = as.name(name1),
               y = as.name(name2))
  ) %>% eval
}

# -------------------------------------------------------------------
# EXAMPLES 1
# -------------------------------------------------------------------

test1(Petal.Width, Petal.Length, iris, 'fred', 'george')
## 	Two-sample Kolmogorov-Smirnov test
## 
## data:  fred and george
## D = 0.66667, p-value < 2.2e-16
## alternative hypothesis: two-sided

# -------------------------------------------------------------------
# Second implementation: use original column names by default.
# -------------------------------------------------------------------
test2 <- function(var1, var2, data,
                  name1 = NULL, name2 = NULL) {
  qvar1 <- enquo(var1)
  qvar2 <- enquo(var2)
  
  if (!is.null(name1)) {
    assign(name1, pull(data, !!qvar1))
    x_name <- as.name(name1)
  } else {
    assign(deparse(substitute(var1)), pull(data, !!qvar1))
    x_name <- as.name(deparse(substitute(var1)))
  }
  
  if (!is.null(name2)) {
    assign(name2, pull(data, !!qvar2))
    y_name <- as.name(name2)
  } else {
    assign(deparse(substitute(var2)), pull(data, !!qvar2))
    y_name <- as.name(deparse(substitute(var2)))
  }
  
  substitute(
    expr = ks.test(x, y),
    env = list(x = x_name,
               y = y_name)
  ) %>% eval
}


# -------------------------------------------------------------------
# EXAMPLES 2
# -------------------------------------------------------------------

test2(Petal.Width, Petal.Length, iris)
## 	Two-sample Kolmogorov-Smirnov test
## 
## data:  Petal.Width and Petal.Length
## D = 0.66667, p-value < 2.2e-16
## alternative hypothesis: two-sided

test2(Petal.Width, Petal.Length, iris, 'fred', 'george')
## 	Two-sample Kolmogorov-Smirnov test
## 
## data:  fred and george
## D = 0.66667, p-value < 2.2e-16
## alternative hypothesis: two-sided