2020-07-24_r_functions.R

library("purrr")

# View(mtcars)
.x <- mtcars[[1]]
mean(.x)
map_dbl(mtcars, ~ mean(.x))
map_dbl(mtcars, mean)

# rnorm()
# args(rnorm)
mean_values <- c(-10, 0, 10, 100)
.x <- mean_values[[1]]
rnorm(n = 10, mean = .x)
map(mean_values, ~ rnorm(n = 10, mean = .x))
map_dfc(mean_values, ~ rnorm(10, mean = .x))


# remotes::install_github("allisonhorst/palmerpenguins")
library("palmerpenguins")
# data(package = 'palmerpenguins')
.x <- penguins[[1]]
length(unique(.x))

map_int(penguins, ~ length(unique(.x)))

n_unique <- function(x) {
    length(unique(x))
}
map_int(penguins, n_unique)



### 2020-08-14
library(ggplot2)
# a list of data frames
by_color <- split(diamonds, diamonds$color)
# a vector of paths
paths <- paste0(names(by_color), ".csv")

library("purrr")
map_dfr(by_color, class)
class(paths)
length(paths)
length(by_color)

# Solve for one
.x <- by_color[[1]]
.y <- paths[[1]]

?write.csv

write.csv(x = .x, file = .y)

map2(by_color, paths, ~ write.csv(x = .x, file = .y))

walk2(by_color, paths, ~ write.csv(x = .x, file = .y))

walk2(by_color, paths, write.csv)

## Won't work because the order of the inputs
## doesn't match the order of the function arguments
walk2(paths, by_color, write.csv)

## You would need to use the full purrr syntax
## with the ~
walk2(paths, by_color, ~ write.csv(x = .y, file = .x))


## 
df <- data.frame(
    a = 1L,
    b = 1.5,
    y = Sys.time(),
    z = ordered(1)
)
df[1:4] %>% sapply(class) %>% str()
df[1:2] %>% sapply(class) %>% str()
df[3:4] %>% sapply(class) %>% str()

df[1:4] %>% map_chr(class) %>% str()
df[1:2] %>% map_chr(class) %>% str()
df[3:4] %>% map_chr(class) %>% str()
# 
# library(IRanges)
# df[1:4] %>% map_chr(~ CharacterList(class(.x)))