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Last data update: 2014.03.03

R: Surface Plots for Two-Way Interactions

DAintfun

R Documentation

Surface Plots for Two-Way Interactions

Description

Makes surface plots to display interactions between two continuous variables

Usage

DAintfun(obj, varnames, theta = 45, phi = 10, xlab=NULL, ylab=NULL, zlab=NULL,...)

Arguments

`obj`	A model object of class `lm`
`varnames`	A two-element character vector where each element is the name of a variable involved in a two-way interaction.
`theta`	Angle defining the azimuthal viewing direction to be passed to `persp`
`phi`	Angle defining the colatitude viewing direction to be passed to `persp`
`xlab`	Optional label to put on the x-axis, otherwise if `NULL`, it will take the first element of `varnames`
`ylab`	Optional label to put on the y-axis, otherwise if `NULL`, it will take the second element of `varnames`
`zlab`	Optional label to put on the z-axis, otherwise if `NULL`, it will be ‘Predictions’
`...`	Other arguments to be passed down to the initial call to `persp`

Details

This function makes a surface plot of an interaction between two continuous covariates. If the model is

y = b[0] + b[1]x1 + b[2]x2 + b[3]x1*x2 + ... + e[i],

this function plots b[1]x1 + b[2]x2 + b[3]x1*x2 for values over the range of X1 and X2. The highest 75%, 50% and 25% of the bivariate density of X1 and X2 (as calculated by sm.density from the sm package) are colored in with colors of increasing gray-scale.

Value

`x1`	Values of the first element of `varnames` used to make predictions.
`x2`	Values of the second element of `varnames` used to make predictions.
`pred`	The predictions based on the values `x1` and `x2`.
`graph`	A graph is produced, but no other information is returned.

Author(s)

Dave Armstrong (UW-Milwaukee, Department of Political Science)

Examples

data(InteractionEx)
mod <- lm(y ~ x1*x2 + z, data=InteractionEx)
DAintfun(mod, c("x1", "x2"))

## Make interactive with:
# mypanel <- function(panel){
# 	DAintfun(mod, c("x1", "x2"), theta=panel$theta, phi=panel$phi)
# 	panel}
# panel <- rp.control(theta=0, phi=25)
# rp.slider(panel, theta, -360, 360, mypanel, showvalue=TRUE)
# rp.slider(panel, phi, 0, 90, mypanel, showvalue=TRUE)

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(DAMisc)
Loading required package: car
Loading required package: effects

Attaching package: 'effects'

The following object is masked from 'package:car':

    Prestige

> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/DAMisc/DAintfun.Rd_%03d_medium.png", width=480, height=480)
> ### Name: DAintfun
> ### Title: Surface Plots for Two-Way Interactions
> ### Aliases: DAintfun
> 
> ### ** Examples
> 
> data(InteractionEx)
> mod <- lm(y ~ x1*x2 + z, data=InteractionEx)
> DAintfun(mod, c("x1", "x2"))
Loading required package: rgl
Loading required package: rpanel
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called 'rpanel'
> 
> ## Make interactive with:
> # mypanel <- function(panel){
> # 	DAintfun(mod, c("x1", "x2"), theta=panel$theta, phi=panel$phi)
> # 	panel}
> # panel <- rp.control(theta=0, phi=25)
> # rp.slider(panel, theta, -360, 360, mypanel, showvalue=TRUE)
> # rp.slider(panel, phi, 0, 90, mypanel, showvalue=TRUE)
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>