Creating a for loop in R

Question

For this project you are required to use an R script to simulate the effectiveness of the t-test. A for loop will be used to carry out the following 2000 times:

Would the loop look something like this

i <- 1
for (i <= 2001) { 
    x <-rf(5,df1=5,df2=10)
    b <- df2
    p.value <-t.test(x,mu=(b/(b-2))$p.value
    i <- i+1
}

Answer 1

In the way you wrote it, it would be a "while" loop.

For loops in R have the following syntax:

for (i in 1:2000) {
    df1 <- 5
    df2 <- 10
    x <-rf(5, df1=df1, df2=df2)
    b <- df2
    p.value <- t.test(x, mu=(b/(b-2)))$p.value
}

Additionally, it might be more efficient to employ an "apply" construct, for example with replicate:

get.p.value <- function() {
        df1 <- 5
        df2 <- 10
        x <-rf(5, df1=df1, df2=df2)
        b <- df2
        p.value <- t.test(x, mu=(b/(b-2)))$p.value
    }
replicate (2000, get.p.value())

This is not always true, but it simplifies the recovery of the p.values.