BIO 226 AUC-MB contrast

References

• Course website http://isites.harvard.edu/icb/icb.do?keyword=k88279
• Lab 3 material http://isites.harvard.edu/fs/docs/icb.topic1100054.files/lab3Slides.pdf
• Book website http://www.hsph.harvard.edu/fitzmaur/ala2e/

Define a function to calcuate \( L \) for AUC-MB contrast

## Define a function to obtain AUCMB contrast
GetAucmbContrast <- function(t) {
    n <- length(t)

    first <- t[1] + t[2] - 2*t[n]
    last  <- t[n] - t[n-1]

    middle <- sapply(seq_len(n-2),
                     FUN = function(i) {                       
                         t[i+2] - t[i]
                     })

    1/2 * c(first, middle, last)
}

Solve examples

Time points 0, 1, 2, 3

## Obtain L for AUC-MB contrast
## This is doing 
## 1/2 * (t_1 + t_2 - 2t_n, t_3 - t_1, t_4 - t2, ..., t_j+1 - t_j-1, ..., t_n - t_n-1)
## L <- 1/2 * c(0 + 1 - 2 * 3, 2 - 0, 3 - 1, 3 - 2)

GetAucmbContrast(c(0,1,2,3))

[1] -2.5  1.0  1.0  0.5

Time points 0, 1, 4, 6

## Obtain L for AUC-MB contrast (example in the text)

GetAucmbContrast(c(0,1,4,6))

[1] -5.5  2.0  2.5  1.0