QQ-Plot of Conditional CDF Values for SPQRx Model

Generates a quantile–quantile (QQ) plot comparing the empirical conditional CDF values from a fitted SPQRx model to the theoretical Uniform(0,1) distribution. If the model is well-calibrated, the points should lie approximately along the 45-degree line.

Usage

eval_plot_qqplot(model, x, y)

Arguments

model

A fitted SPQR or SPQRx model object.

x

A matrix or data frame of covariates used for prediction.

y

A numeric response vector corresponding to x.

Value

A ggplot2 object representing the QQ-plot.

Details

The function computes conditional CDF values using predict_spqrx(..., type = "CDF") and compares the sorted empirical CDF values against theoretical Uniform(0,1) quantiles.

This diagnostic assesses overall distributional calibration. Deviations from the 45-degree line indicate model misspecification or poor fit in certain regions of the conditional distribution.

Examples

if (FALSE) { # \dontrun{
fit <- spqrx(...)
p <- eval.plot.qqplot(fit, x_test, y_test)
print(p)
} # }