Today's thoughts: I can't fully grasp the assignment

 

So I've been mulling on this assignment for almost four hours, and I can't seem to fully understand how to execute the Extended Cox Proportional Hazards Model. I understand the concept, but I'm not sure if I'm understanding the dataset. What we're analyzing here is the Stanford Heart Transplant Data. Our main goal is to assess whether patients receiving transplants survived longer than patients not receiving heart transplants. 

In survival data analysis, there are two functions in your equation: 1) the survival function; and 2) the hazard function. If you know either of the functions, you can determine the other. While it is more appealing to directly determine the survival function, it is usually the hazard function we are interested in identifying due to mathematical reasons. There are two models that can be used: the Kaplan-Meier model, or a Cox Proportional Hazards (PH) model to estimate survival times. The former estimates survival probabilities (i.e. the survival function) while the latter estimates hazard ratios (i.e. the hazard function). Because of this, and also because if our model is semi-parametric, we would use Cox PH model.

Now in this assignment we are to use a Cox PH model, but the approach is an EXTENDED Cox PH model (the other approach is using a STRATIFIED Cox PH model). I am getting confused as to which variables should be included in my model as the variables are not straightforwardly explained in the assignment dossier or in the book. Also, I am a bit confused what my heaviside functions should be, and what code should I type in to determine my heaviside functions (yes, that's the correct spelling of heaviside. It's a mathematical term. Look it up on Google). Argh! I'm just frustrated because I was hoping to finish this assignment today and ended up not finishing it. Though I'm glad I was able to understand the extended Cox PH model, but I failed to execute the codes. It's frustrating. And I still have a number of other assignments that I need to do. I was hoping I can cross this one off but I guess I I have to park it until Monday.

Times like this I just want to throw a chair out of the window to release stress. I can't help but think I wasted time. I know I shouldn't say this because I learned something new and I know I'm now prepared to ask questions by Monday from our instructor. Nonetheless, it's just a bothersome feeling not to have finished this assignment.

Oh well. Let's move on to the next assignment (I have three more lined up, UGH).

Until then,