qwraps2 (version 0.2.3)

qroc: Receiver Operator Curves

Description

Construction of ROC curves.

Usage

qroc(x, ...)
qroc_build_data_frame(fit, n_threshold = 200)
auc(.data)

Arguments

x

a glm fit or data.frame generated by qroc_build_data_frame.

...

Ignored

fit

a glm fit with family = binomial().

n_threshold

number of thresholds to test against.

.data

a data.frame generated by qroc_build_data_frame.

Value

a ggplot. Minimal aesthetics have been used so that the user may modify the graphic as desired with ease.AUC for the data set generated by

Details

Given a glm fit with family = "binomial" (either a log-link or logit-link should be fine, a data set will be constructed and ROC plots generated.

The area under the curve (AUC) is determined by a trapezoid approximation.

Examples

## Not run: 
# # load ggplot2 and the diamonds data set
# library(ggplot2)
# data(diamonds, package = "ggplot2")
# 
# # Create two logistic regression models
# fit1 <- glm(I(price > 2800) ~ cut * color, data = diamonds, family = binomial())
# fit2 <- glm(I(price > 2800) ~ cut + color + clarity, data = diamonds, family = binomial())
# 
# # Easiest way to get an ROC plot:
# qroc(fit1)
# qroc(fit2)
# 
# # Create two data sets, this will also let you get the AUC out
# data1 <- qroc_build_data_frame(fit1)
# data2 <- qroc_build_data_frame(fit2)
# 
# auc(data1)
# auc(data2)
# 
# # Plotting the ROC from the data set can be done too
# qroc(data1)
# 
# # Add the AUC value to the plot title
# qroc(data2) + ggtitle(paste("Fit 2\nAUC =", round(auc(data2), 2)))
# 
# # build a data set for plotting to ROCs on one plot
# plot_data <- rbind(cbind(Model = "fit1", data1),
#                    cbind(Model = "fit2", data2))
# qroc(plot_data) + aes(color = Model) 
# 
# # with AUC in the legend
# plot_data <- rbind(cbind(Model = paste("Fit1\nauc =", round(auc(data1), 3)), data1),
#                    cbind(Model = paste("Fit2\nauc =", round(auc(data2), 3)), data2))
# qroc(plot_data) + 
#   theme_bw() + 
#   aes(color = Model, linetype = Model) +
#   theme(legend.position   = "bottom", 
#         legend.text.align = 0.5)
# ## End(Not run)