Why use apply?

Intermediate R for Finance

Lore Dirick

Manager of Data Science Curriculum at Flatiron School

Meet the apply family

Function	Description
apply	Apply functions over array margins
lapply	Apply a function over a list or vector
eapply	Apply a function over values in an environment
mapply	Apply a function to multiple lists or vector arguments
rapply	Recursively apply a function to a list
tapply	Apply a function over a ragged array
sapply	Simplify the result from lapply
vapply	Strictly simplify the result from lapply

Function	Description
apply	Apply functions over array margins
lapply	Apply a function over a list or vector
eapply	Apply a function over values in an environment
mapply	Apply a function to multiple lists or vector arguments
rapply	Recursively apply a function to a list
tapply	Apply a function over a ragged array
sapply	Simplify the result from lapply
vapply	Strictly simplify the result from lapply

Function	Description
apply	Apply functions over array margins
lapply	Apply a function over a list or vector
eapply	Apply a function over values in an environment
mapply	Apply a function to multiple lists or vector arguments
rapply	Recursively apply a function to a list
tapply	Apply a function over a ragged array
sapply	Simplify the result from lapply
vapply	Strictly simplify the result from lapply

stock_list <- list(stock_name = "Apple", ticker = "AAPL", 
                   price = 126.5, good_deal = TRUE)

lapply(stock_list, FUN = class)

$stock_name
"character"

$ticker
"character"

$price
"numeric"

$good_deal
"logical"

ch5_vid1_slides.015.png

ch5_vid1_slides.016.png

ch5_vid1_slides.017.png

$sharpe = \frac{mean(r) - r_f}{sd(r)}$

Intermediate R for Finance