Practical exercise 1
In this exercise we will see how Nelson-Aalen plots may be used to study the effect of various covariates for the melanoma data given at the course web-page.
You may read the data into R by the command:
melanoma=read.table("http://www.uio.no/studier/emner/matnat/math/STK4080/h12/melanoma.txt", header=T)
We will make Nelson-Aalen plots for the mortality from melanoma treating death from other causes as censoring.
At the lectures we showed how one may obtain Nelson-Aalen plots for females and males. The R code we used to obtain these plots is given under computing at the course web-page.
a) Make Nelson-Aalen plots for patients with ulceration present and absent and interpret the results. (Ulceration is "present" if the surface of the tumor viewed in a microscope show signs of ulcers and "absent" otherwise.)
b) Make Nelson-Aalen plots for the three thickness groups 0-