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Bootstrapping a Single Statistic (k=1)
The following example generates the bootstrapped 95% confidence interval for R-squared in the linear regression of miles per gallon (mpg) on car weight (wt) and displacement (disp). The data source is mtcars. The bootstrapped confidence interval is based on 1000 replications.
# Bootstrap 95% CI for R-Squared
library(boot)
# function to obtain R-Squared from the data
rsq = function(formula, data, indices) {
d = data[indices,] # allows boot to select sample
fit = lm(formula, data=d)
return(summary(fit)$r.square)
}
# bootstrapping with 1000 replications
results = boot(data=mtcars, statistic=rsq,
R=1000, formula=mpg~wt+disp)
# view results
results
plot(results)
# get 95% confidence interval
boot.ci(results, type="bca")
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