Where does the bootstrap standard error live in the boot class?

Question

Consider the following bootstrap:

library(MASS)
library(boot)

# c)
set.seed(1)
boot.fn= function(data, index) mean(data[index])
output=boot(Boston$medv, boot.fn, 1000)

If we run print(output), we get

Call:
boot(data = Boston$medv, statistic = boot.fn, R = 1000)


Bootstrap Statistics :
    original      bias    std. error
t1* 22.53281 0.008517589   0.4119374

However, when I examine the output object, I cannot find values representing the bootstrap statistics. Where is original, bias and std. error in the actual output object returned by boot?

Answer 1

They are calculated by print.boot and not stored in the boot object. Look at getAnywhere(print.boot) for the details.

You can either calculate these values yourself or use capture.output.

For your example:

#original:
output$t0
#bias:
mean(output$t)-output$t0
#se: 
sd(output$t)

Answer 2

This command seems to work:

apply(output$t,2,sd)[1]