plot-methods {twopartm}

Method for Function plot for Two-part Model Objects in Package twopartm

Description

The plot method for twopartm-class that provides plot diagnostics for a fitted two-part regression model object of class twopartm.

Usage

## S4 method for signature 'twopartm,missing'
plot(x, y, ...)

Arguments

x

an object of class twopartm.

y

not used.

...

arguments passed to plot.lm in the default setup.

Details

The plot method for twopartm-class returns the residual plot for the full two-part model, and also six plots for each part's glm model. Six plots are: a plot of residuals against fitted values, a Scale-Location plot of sqrt(| residuals |) against fitted values, a Normal Q-Q plot, a plot of Cook's distances versus row labels, a plot of residuals against leverages, and a plot of Cook's distances against leverage/(1-leverage). By default, the first three plots and the fifth one of each part's model are provided. The plots for each part's model could be selected by argument which of function plot.lm for glm model object.

Value

Returns residual plot for the full two-part model, and plot diagnostics for each part's model from an object twopartm.

Author(s)

Yajie Duan, Birol Emir, Griffith Bell and Javier Cabrera

References

Belotti, F., Deb, P., Manning, W.G. and Norton, E.C. (2015). twopm: Two-part models. The Stata Journal, 15(1), pp.3-20.

Belsley, D. A., Kuh, E. and Welsch, R. E. (1980). Regression Diagnostics. New York: Wiley.

Cook, R. D. and Weisberg, S. (1982). Residuals and Influence in Regression. London: Chapman and Hall.

See Also

twopartm-class, glm,plot.lm, tpm

Examples

##data about health expenditures, i.e., non-negative continuous response
data(meps,package = "twopartm")


##fit two-part model with the same regressors in both parts, with logistic
##regression model for the first part, and glm with Gamma family with log
##link for the second-part model
tpmodel = tpm(exp_tot~female+age, data = meps,link_part1 = "logit",
family_part2 = Gamma(link = "log"))

tpmodel

##summary information
summary(tpmodel)

##plots for two-part model
plot(tpmodel)