11.13 Proportional Hazards

The proportional hazards assumption states that (ISLR2 11.14):

h(t|xi)=h0(t)exp(pj=1xijβk)

Assumes separate time dependence (baseline hazard h0) from feature dependence.

  • Important to check proportional assumption!

    • Qualitative feature: plot the log hazard function for each level of the feature

    • Quantitative feature: stratify (cut) the feature and do the above.

Source ISLR Fig 11.4