nest: Apply a function recursively

In parksw3/wolframR: Functions from the Wolfram language

Description

Implementation of the Nest function from the Wolfram language. Syntax order has been changed so that the function is compatible with the pipe operator (see %>%).

Usage

nest(x, expr, n, m = 1, xname = "x")

Arguments

x	an object or a variable name.
expr	an expression or a function to be evaluated recursively.
n	number of iterations.
m	return results of the last m iterations. Setting m = "all" returns a list of all results. This is equivalent to NestList function from the Wolfram language.
xname	character string containing the name of the argument that will be used recursively.

Value

a list or a vector of length m containing the results or a function; list of functions will be returned if m > 1.

Examples

## Some of these examples are directly taken from the Wolfram documentation

## Newton iterations for \sqrt{2}
nest(1, (x + 2/x)/2, 5)

## Last two terms of the Fibonacci sequence
nest(c(1, 1), c(x[2], x[1] + x[2]), 10, m = "all")

## Gray codes of length 4
nest(0, c(x, length(x) + rev(x)), 4)

## Multi-log transformation
multi_log <- nest(x, log(x + 1), 4)

## Changing xname can imitate the use of '#' in the Wolfram language
## Both codes return a function. How are they different?
f1 <- nest(x, x^y, 4, xname = "y")
f2 <- nest(x, y^x, 4, xname = "y")

parksw3/wolframR documentation built on May 24, 2019, 6:16 p.m.