plot.gofGroup: Plot Results of Group Goodness-of-Fit Test

Description

Plot the results of calling the function gofGroupTest, which returns an object of class "gofGroup" when performing a goodness-of-fit test to determine whether data in a set of groups appear to all come from the same probability distribution (with possibly different parameters for each group). Five different kinds of plots are available. The function plot.gofGroup is automatically called by plot when given an object of class "gofGroup". The names of other functions associated with goodness-of-fit test are listed under Goodness-of-Fit Tests.

Usage

## S3 method for class 'gofGroup':
plot(x, plot.type = "Summary", 
    captions = list(QQ = NULL, MDQQ = NULL, ScoresQQ = NULL, ScoresMDQQ = NULL, 
      Results = NULL), 
    x.labels = list(QQ = NULL, MDQQ = NULL, ScoresQQ = NULL, ScoresMDQQ = NULL), 
    y.labels = list(QQ = NULL, MDQQ = NULL, ScoresQQ = NULL, ScoresMDQQ = NULL), 
    same.window = FALSE, ask = same.window & plot.type == "All", add.line = TRUE, 
    digits = ifelse(plot.type == "Summary", 2, .Options$digits), test.result.font = 1, 
    test.result.cex = ifelse(plot.type == "Summary", 0.9, 1) * par("cex"), 
    test.result.mar = c(0, 0, 3, 0) + 0.1, individual.p.values = FALSE, 
    cex.main = ifelse(plot.type == "Summary", 1.2, 1.5) * par("cex"), 
    cex.axis = ifelse(plot.type == "Summary", 0.9, 1) * par("cex"), 
    cex.lab = ifelse(plot.type == "Summary", 0.9, 1) * par("cex"), 
    main = NULL, xlab = NULL, ylab = NULL, xlim = NULL, ylim = NULL, add.om.title = TRUE, 
    oma = if (plot.type == "Summary" & add.om.title) c(0, 0, 5, 0) else c(0, 0, 0, 0), 
    om.title = NULL, om.font = 2, om.cex.main = 1.5 * par("cex"), om.line = 1, ...)

Arguments

an object of class "gofGroup". See gofGroup.object for details.

plot.type

character string indicating what kind of plot to create. Only one particular plot type will be created, unless plot.type="All", in which case all plots will be created sequentially. The possible values of plot.type are:

captions

a list with 1 to 5 components with the names "QQ", "MDQQ", "ScoresQQ", "ScoresMDQQ", and/or "Results". Each component either has the value NULL or else it is a char

x.labels

a list of 1 to 4 components with the names "QQ", "MDQQ", "ScoresQQ", and/or "ScoresMDQQ". Each component either has the value NULL or else it is a character string containing th

y.labels

a list of 1 to 4 components with the names "QQ", "MDQQ", "ScoresQQ", and/or "ScoresMDQQ". Each component either has the value NULL or else it is a character string containing the lab

same.window

logical scalar indicating whether to produce all plots in the same graphics window (same.window=TRUE), or to create a new graphics window for each separate plot (same.window=FALSE; the default). The argument is relev

ask

logical scalar supplied to the function devAskNewPage, indicating whether to prompt the user before creating a new plot within a single graphics window. The default value is FALSE

add.line

logical scalar indicating whether to add a line to the plot. If add.line=TRUE and plot.type="Q-Q Plot" or plot.type="Scores Q-Q Plot", a 0-1 line is added to the plot. If add.line=TRUE and

digits

scalar indicating how many significant digits to print for the test results when plot.type="Summary" or plot.type="Test Results". If plot.type == "Summary", the default value is digits=2, ot

individual.p.values

logical scalar indicating whether to display the p-values associated with each individual group. The default value is individual.p.values=FALSE.

test.result.font

numeric scalar indicating which font to use to print out the test results. The default value is test.result.font=1. See the description of the font argument in the help file for par

test.result.cex

numeric scalar indicating the value of cex to use to print out the test results. The default value is 0.9*par("cex") when plot.type="Summary", otherwise it is par("cex"). See the description

test.result.mar

numeric vector indicating the value of mar to use to print out the test results. The default value is test.result.mar=c(0, 0, 3, 0)+0.1. See the description of the mar argument in the help file for

add.om.title

logical scalar indicating whether to add a title in the outer margin when plot.type="Summary". The default value is add.om.title=TRUE.

om.title

character string containing the outer margin title. The default value is om.title=NULL, which will result in a default title.

om.font

numeric scalar indicating the font to use for the outer margin. The default value is om.font=2.

om.cex.main

numeric scalar indicating the value of cex for the outer margin title. The default value is 1.5 * par("cex").

om.line

numeric scalar indicating the line to place the outer margin title on. The default value is om.line=1.

cex.main, cex.axis, cex.lab, main, xlab, ylab, xlim, ylim, oma, ...

additional graphics parameters. See the help file for par.

Value

plot.gofGroup invisibly returns the first argument, x.

Details

The function plot.gofGroup is a method for the generic function plot for the class "gofGroup" (see gofGroup.object). It can be invoked by calling plot and giving it an object of class "gofGroup" as the first argument, or by calling plot.gofGroup directly, regardless of the class of the object given as the first argument to plot.gofGroup. Plots associated with the goodness-of-fit test are produced on the current graphics device. These can be one or all of the following:

plot.type="Q-Q Plot". Q-Q Plot of observed p-values vs. quantiles from aUniform [0,1] distribution. See the help file forqqPlot.
plot.type="Tukey M-D Q-Q Plot". Tukey mean-difference Q-Q plot for observed p-values and quantiles from aUniform [0,1] distribution. See the help file forqqPlot.
plot.type="Scores Q-Q Plot". Q-Q Plot of Normal scores vs. quantiles from aNormal(0,1) distributionor Q-Q Plot of Chisquare scores vs. quantiles from aChisquare distributionwith 2 degrees of freedom. See the help file forqqPlot.
plot.type="Scores Tukey M-D Q-Q Plot". Tukey mean-difference Q-Q plot based on Normal scores or Chisquare scores. See the help file forqqPlot.
Results of the goodness-of-fit test (plot.type="Test Results"). See the help file forprint.gofGroup.

See the help file for gofGroupTest for more information.

References

Chambers, J. M. and Hastie, T. J. (1992). Statistical Models in S. Wadsworth & Brooks/Cole.

Examples

Run this code

# Create an object of class "gofGroup" then plot it.

  # Example 10-4 of USEPA (2009, page 10-20) gives an example of 
  # simultaneously testing the assumption of normality for nickel 
  # concentrations (ppb) in groundwater collected at 4 monitoring 
  # wells over 5 months.  The data for this example are stored in 
  # EPA.09.Ex.10.1.nickel.df.

  EPA.09.Ex.10.1.nickel.df
  #   Month   Well Nickel.ppb
  #1      1 Well.1       58.8
  #2      3 Well.1        1.0
  #3      6 Well.1      262.0
  #...
  #18     6 Well.4       85.6
  #19     8 Well.4       10.0
  #20    10 Well.4      637.0


  # Test for a normal distribution at each well:
  #--------------------------------------------

  gofGroup.obj <- gofGroupTest(Nickel.ppb ~ Well, 
    data = EPA.09.Ex.10.1.nickel.df)

  dev.new()
  plot(gofGroup.obj)

  # Make your own titles for the summary plot
  #------------------------------------------
  dev.new()
  plot(gofGroup.obj, captions = list(QQ = "Q-Q Plot", 
    ScoresQQ = "Scores Q-Q Plot", Results = "Results"),
    om.title = "Summary Plot")

  # Just the Q-Q Plot
  #------------------
  dev.new()
  plot(gofGroup.obj, plot.type="Q-Q")


  # Make your own title for the Q-Q Plot
  #-------------------------------------
  dev.new()
  plot(gofGroup.obj, plot.type="Q-Q", main = "Q-Q Plot")

  #==========

  # Clean up
  #---------
  rm(gofGroup.obj)
  graphics.off()

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