Prefilling functions

Intermediate Functional Programming with purrr

Colin Fay

Data Scientist & R Hacker at ThinkR

Using partial()

Prefill a function:

mean_na_rm <- partial(mean, na.rm = TRUE)
mean_na_rm( c(1,2,3,NA) )

lm_iris <- partial(lm, data = iris)
lm_iris(Sepal.Length ~ Sepal.Width)

Call:
lm(formula = ..1, data = iris)
Coefficients:
(Intercept)  Sepal.Width  
     6.5262      -0.2234

mean(airquality$Ozone, na.rm = TRUE)
mean(mtcars$mpg, na.rm = TRUE)
mean(iris$Petal.Width, na.rm = TRUE)

mean_na_rm <- partial(mean, na.rm = TRUE)
mean_na_rm(airquality$Ozone)
mean_na_rm(mtcars$mpg)
mean_na_rm(iris$Sepal.Length)

partial() & compose()

rounded_mean <- compose(
  partial(round, digits = 2), 
  partial(mean, na.rm = TRUE)
)
rounded_mean(airquality$Ozone)

42.13

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Intermediate Functional Programming with purrr