R: Function to draw a multivari chart

multivari {plotrix}

R Documentation

Function to draw a multivari chart

Description

A multivari chart of one quantitative response variable depending on two to four categorical variables can be drawn.

Usage

multivari(var, fac1, fac2, fac3 = NULL, fac4 = NULL, data, sort = FALSE,
 fun = mean, pch = list(15, 16, 17), col = list("black", "blue", "red"),
 col0 = "black", cex = 1, fac.cex = 2, xlab.depth = 3, legend = FALSE,
 main = paste("multivari chart of", var), ...)

Arguments

`var`	variable name (character string) or column index of response variable, required
`fac1`	variable name (character string) or column index of first level factor, required
`fac2`	variable name (character string) or column index of second level factor, required
`fac3`	variable name (character string) or column index of third level factor, optional
`fac4`	variable name (character string) or column index of fourth level factor, optional; can only be specified if there is also a third level factor; separate multivari charts for the first three factors are drawn for each level of this factor
`data`	a data frame, required
`sort`	logical, specifying whether or not levels are sorted, when converting character vectors to factors (a single choice for all factors is needed); default: `FALSE`
`fun`	a function to be used in aggregation; default: `mean`
`pch`	a list of length 2 or 3, depending on whether or not `fac3` is specified; the ith list element can be an individual plotting symbol (like the usual `pch` entry) or a vector of plot symbols for each level of `fac_i`
`col`	a list of length 2 or 3, depending on whether or not `fac3` is specified; the ith list element can be an individual color or a vector of colors for each level of `fac_i`; this color specification is used for the plot symbols of `fac_i` levels and for the lines connecting the symbols for the next level in the hierarchy
`col0`	the color for the first line to be drawn
`cex`	the size of the annotation text below the horizontal axis (annotation of the fourth level header is 1.5 times this size)
`fac.cex`	a multiplier for `cex`; plot symbol sizes are `fac.cex*cex`; default: 2
`xlab.depth`	labels for the horizontal axis are printed down to this level of the hierarchy (default: 3); if the depth is reduced, different plot symbols should be used, and a legend should be drawn
`legend`	logical determining whether or not a legend should be drawn (default: FALSE); the function determines wether top right or bottom right yields a better position (it is not guaranteed that there is no overlab); if this does not work well, one can manually draw a legend in the outer margin
`main`	title, as usual; a default is provided
`...`	further arguments to functions `plot`, `lines`, `points`, `mtext`

Details

A multivari chart as implemented here mainly serves exploratory purposes. It works particularly well with balanced data, and it serves the purpose to visualize an interaction of degree up to four. The order of the factors can make a big difference in the display. If there is no natural order, it may be worthwhile inspect several orders.

The function is inspired by Minitabs behavior for multivari charts. It does not attempt to visualize individual observations.

For interactions with two factors only, it is often preferrable to use function interaction.plot.

Value

a list of (lists of) data frames with summary statistics to be plotted

Author(s)

Ulrike Groemping

Examples

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.
## Not run: 
require(car)
multivari("cycles", "len", "load", "amp", data=Wool, 
    col=list("black","red",c("grey70","grey45","grey20")),
    pch=list(15,17,8), legend=TRUE, xlab.depth = 2, lwd=2)
multivari("cycles", "load", "len", "amp", data=Wool, 
    col=list("black",c("red","blue","darkgreen"),
    c("grey70","grey45","grey20")),
    pch=list(15,17,8), legend=TRUE, xlab.depth = 2, lwd=2)
    
## create a fake fourth factor
fakedat <- rbind(cbind(newfac="blabla",Wool),cbind(newfac="albalb",Wool))
## make it character for demonstrating the effect of sort option
fakedat$newfac <- as.character(fakedat$newfac)

## default: sort order in the data is respected (order of unique is used)
multivari("cycles", "load", "len", "amp", "newfac", data=fakedat, 
    col=list("black",c("red","blue","darkgreen"),
    c("grey70","grey45","grey20")),
    pch=list(15,17,8), legend=TRUE, xlab.depth = 2, lwd=2, cex=0.8)
    
## sort=TRUE: levels are sorted (order of sort(unique))
multivari("cycles", "load", "len", "amp", "newfac", data=fakedat, 
    col=list("black",c("red","blue","darkgreen"),
    c("grey70","grey45","grey20")),
    pch=list(15,17,8), legend=TRUE, xlab.depth = 2, lwd=2, cex=0.8,
    sort=TRUE)

## End(Not run)

[Package plotrix version 3.7 Index]