halfnorm: Half normal plot with simulated envelopes
In binomTools: Performing diagnostics on binomial regression models

Description Usage Arguments Details Value Author(s) References See Also Examples

View source: R/halfnorm.R

halfnorm produces a half normal plot of the residuals with simulated envelopes useful for model evaluation and detection of outliers

halfnorm(object, resType = c("approx.deletion", "exact.deletion",
         "standard.deviance", "standard.pearson", "deviance",
         "pearson", "working", "response", "partial"), env = T,
         nsim = 20, plot = T, identify = F, n = 2)

`object`	An object of class `glm` with a binomial family
`resType`	The type of residual used in the plot
`env`	Logical for whether envelopes are simulated
`nsim`	Number of simulations used for the envelopes
`plot`	Logical for whether the points should be plotted. If `plot = F` a list is returned
`identify`	Logical for whether it should be possible to identify points interactively. Ignored if `plot = F`
`n`	How many points should be identified. Ignored if `identify = F`

Absolute values of the residuals are used in a half normal plot that otherwise corresponds to a regular normal probability plot.

Residuals from a binomial glm are not necessarily uncorrelated and normally distributed and may accordingly deviate from a straight line even if the fitted model is true. If the fitted model is true the optional simulated envelopes are likely to contain the absolute residuals.

The different types of residuals are described in Residuals

If plot = T a plot is produced. Otherwise a list of the residuals and their expected values are returned

Merete K Hansen

Atkinson, A. C. (1981) Two graphical displays for outlying and influential observations in regression. Biometrika, 68, 13-20.

Collett, D. (2003) Modelling binary data. Second edition. Chapman & Hall/CRC.

Residuals, identify

## Halfnormal plot with simulated envelopes
data(beetles)
beetles.glm <- glm(cbind(y, n-y) ~ conc, family=binomial, data=beetles)
halfnorm(beetles.glm, resType='pearson')

## Not run: 
## Halfnormal plot with simulated envelopes
## Two points are interactively identified when they are selected with the mouse
halfnorm(beetles.glm, resType='deviance', identify = T, n = 2)

## End(Not run)