The output function will output an observation
from a datastep. The function takes no parameters. To use
the function, simply call it on the rows you want to output. Typically
it is called within a conditional. The output function is interesting
in that you can output multiple rows for the same input observation.
output()Observation is marked with a output flag. No return value.
#' # Example 1: Output all cars that are 4 cylinder
df <- datastep(mtcars,
keep = c("mpg", "cyl", "disp"), {
if (cyl == 4)
output()
})
df
# mpg cyl disp
# 1 22.8 4 108.0
# 2 24.4 4 146.7
# 3 22.8 4 140.8
# 4 32.4 4 78.7
# 5 30.4 4 75.7
# 6 33.9 4 71.1
# 7 21.5 4 120.1
# 8 27.3 4 79.0
# 9 26.0 4 120.3
# 10 30.4 4 95.1
# 11 21.4 4 121.0
# Example 2: Output two rows for each 6 cylinder car
# Prepare sample data
dat <- data.frame(name = rownames(mtcars), mtcars, stringsAsFactors = FALSE)
# Perform datastep
df <- datastep(dat,
keep = c("name", "mpg", "cyl", "disp", "seq"), {
if (cyl == 6) {
seq <- 1
output()
seq <- 2
output()
}
})
df
# name mpg cyl disp seq
# 1 Mazda RX4 21.0 6 160.0 1
# 2 Mazda RX4 21.0 6 160.0 2
# 3 Mazda RX4 Wag 21.0 6 160.0 1
# 4 Mazda RX4 Wag 21.0 6 160.0 2
# 5 Hornet 4 Drive 21.4 6 258.0 1
# 6 Hornet 4 Drive 21.4 6 258.0 2
# 7 Valiant 18.1 6 225.0 1
# 8 Valiant 18.1 6 225.0 2
# 9 Merc 280 19.2 6 167.6 1
# 10 Merc 280 19.2 6 167.6 2
# 11 Merc 280C 17.8 6 167.6 1
# 12 Merc 280C 17.8 6 167.6 2
# 13 Ferrari Dino 19.7 6 145.0 1
# 14 Ferrari Dino 19.7 6 145.0 2
# Example 3: Create data frame using output() functions
df <- datastep(data.frame(), {
# Row 1
COL1 <- 1
COL2 <- "One"
output()
# Row 2
COL1 <- 2
COL2 <- "Two"
output()
})
df
# COL1 COL2
# 1 1 One
# 2 2 Two