Plot residuals for a fitted mixture of linear regressions.

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Description

Plots the residuals against predictors or fitted values using symbols whose size is proportional to the probability that the associated observation was generated by the associated component of the model.

Usage

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## S3 method for class 'mresid'
plot(x, vs.fit=FALSE, whichx=1, shape="disc",
            ngon=20, size=1, xlab=NULL, ...)

Arguments

x

A list with components containing the residuals, the relevant probabilities, the predictors, and the observations, as returned by resid.mix(). When plotting against fitted values, it is probably better to used the standardized residuals, i.e. resid.mix() should be called with std=TRUE.

vs.fit

Logical argument. If TRUE the residuals are plotted versus the fitted values.

whichx

Indicates which predictor to plot against if there is more than one; i.e. indicates which column of the x matrix to use. If vs.fit is TRUE, whichx is ignored.

shape

The shape of the plotting symbol; possible values are "disc", "square", and "diamond". Partial matching is used so only the first few letters need be given.

ngon

The "disc" shape is actually a regular polygon; ngon specifies how many sides it should have; ignored if shape is not equal to "disc".

size

A scale factor to change the absolute sizes of the plotting symbols; values larger than 1 make the symbols larger; values less than 1 make them smaller.

xlab

The x label for the plot; defaults to "x".

...

Additional arguments to be passed to the polygon function which actually draws the plotting symbols.

Details

This function is a "method" for plot. The plot produced is visually assessed by ignoring or discounting small symbols.

Side Effects

A residual plot is produced in whatever device is currently open.

ACKNOWLEDGEMENT

The idea of creating residual plots for regression mixtures by making the symbol size proportional to the associated probability is due to Adrian Baddeley of the University of Western Australia.

Author(s)

Rolf Turner r.turner@auckland.ac.nz http://www.stat.auckland.ac.nz/~rolf

References

Turner, T. R. (2000) Estimating the rate of spread of a viral infection of potato plants via mixtures of regressions. Appl. Statist. vol. 49, Part 3, pp. 371 – 384.

See Also

bootcomp, cband, covmix, mixreg, plot.cband, qq.mix, resid.mix

Examples

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#See \link{mixreg} for examples.