Residuals for regression models with zero-inflated outcomes

Caluates the DPIT residuals for a regression model with zero-inflated discrete outcome. A zero-inflated model from pscl is used in this function.

Usage

resid_zeroinfl(model, plot=TRUE, scale='normal')

Arguments

model: Model object, which is the output of pscl::zeroinfl.
plot: A logical value indicating whether or not to return QQ-plot.
scale: You can choose the scale of the residuals among normal and uniform scales. The default scale is normal.

Value

DPIT residuals. If plot=TRUE, also produces a QQ plot.

References

Yang, Lu. "Double Probability Integral Transform Residuals for Regression Models with Discrete Outcomes." arXiv preprint arXiv:2308.15596 (2023).

Examples

## Zero-Inflated Poisson
library(pscl)
n <- 500
set.seed(1234)
# Covariates
x1 <- rnorm(n)
x2 <- rbinom(n, 1, 0.7)
# Coefficients
beta0 <- -2
beta1 <- 2
beta2 <- 1
beta00 <- -2
beta10 <- 2

# Mean of Poisson part
lambda1 <- exp(beta0 + beta1 * x1 + beta2 * x2)
# Excess zero probability
p0 <- 1 / (1 + exp(-(beta00 + beta10 * x1)))
## simulate outcomes
y0 <- rbinom(n, size = 1, prob = 1 - p0)
y1 <- rpois(n, lambda1)
y <- ifelse(y0 == 0, 0, y1)
## True model
modelzero1 <- zeroinfl(y ~ x1 + x2 | x1, dist = "poisson", link = "logit")
resid.zero1 <- resid_zeroinfl(modelzero1, plot = TRUE, scale = "uniform")


## Zero inflation
modelzero2 <- glm(y ~ x1 + x2, family = poisson(link = "log"))
resid.zero2 <- resid_disc(modelzero2, plot = TRUE, scale = "normal")