####### Computing and plotting confidence bands for
####### logistic regression
####### (Unfortunately need a custom function at this point,
####### since it is not handled by mosaic yet)
library("mosaic")
library("Stat2Data")
data("MedGPA")
### Fit the model
medschool.model <-
glm(Acceptance ~ MCAT, data = MedGPA, family = "binomial")
summary(medschool.model)
### Get the custom function
source("http://colindawson.net/stat215/code/logistic_interval_function.R")
### The usage pattern of the function
# plot.logistic.bands(
# model, # the logistic model object
# xname, # name of the predictor
# xlim, # range of x values to plot
# xlab, # label to use on X axis
# ylab # label to use on Y axis
# level # confidence level (0 to 1 scale)
# )
plot.logistic.bands(
model = medschool.model,
xname = "MCAT",
xlim = range(~MCAT, data = MedGPA),
xlab = "MCAT Score",
ylab = "P(Acceptance)",
level = 0.95
)
points(Acceptance ~ MCAT, data = MedGPA)
### Fit a model with multiple predictors and get a confidence
### interval for a prediction at specific x values
model2 <- glm(Acceptance ~ MCAT + GPA, data = MedGPA)
get.logistic.CI(model2, level = 0.95, MCAT = 34, GPA = 3.5)