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Last data update: 2014.03.03

R: Multidimensional step functions

multistep

R Documentation

Multidimensional step functions

Description

Produces a multistep object

Usage

multistep(coefchain,x=NULL,intercept=0,sortedx = apply(x,2,sort),names = NULL, pinters=NULL,...)

Arguments

`coefchain`	Vector of step sizes at each observation point for each vector, concatentated as a single vector.
`x`	Matrix of observations coefchain corresponds to.
`intercept`	Intercept value. i.e. value of mean(f(x)).
`sortedx`	x sorted in each column.
`names`	Names to be assigned to covariates.
`pinters`	The values of the component functions at the left ends of each range.
`...`	Additional variables to be stored in the final object.

Details

This function generates a multistep object, to represent a function that is the sum of right-continuous step functions on each input. Internally, the function is stored in a sparse format.

sortedx and pinters are calculated, if not provided.

Multistep objects may be plotted. They may also be evaluated at a particular vector value, or matrix of values, through the * operator or the predict function.

Value

Produces a multistep object.

Author(s)

Zhou Fang

Examples

## Produces a 2d step function

set.seed(79)
n <- 100; p <- 2

## Pick some random knots
x <- matrix(runif(n * p, min = -2.5, max = 2.5), nrow = n, ncol = p)
obj = multistep(rep(0.1, (n-1)*p), x)
x2 <-  matrix(runif(n * p, min = -2.5, max = 2.5), nrow = n, ncol = p)
obj * x2 - obj*x
image( outer(-50:50/10, -50:50/10, function(x,y) obj*c(x,y)))