SAS user-defined functions to calculate statistical power for cluster randomized trial with survival outcome

I implemented three calculation methods based on papers listed below.

function:sample_size_CLR

Gangnon, Ronald E., and Michael R. Kosorok. "Sample‐size formula for clustered survival data using weighted log‐rank statistics." Biometrika 91.2 (2004): 263-275.

https://www.jstor.org/stable/20441100?seq=1#page_scan_tab_contents

function:sample_size_SFM

Jahn‐Eimermacher, Antje, Katharina Ingel, and Astrid Schneider. "Sample size in cluster‐randomized trials with time to event as the primary endpoint." Statistics in medicine 32.5 (2013): 739-751.

https://www.ncbi.nlm.nih.gov/pubmed/22865817

function:sample_size_LWM

XIE, Tailiang; WAKSMAN, Joel. Design and sample size estimation in clinical trials with clustered survival times as the primary endpoint. Statistics in medicine, 2003, 22.18: 2835-2846.

http://onlinelibrary.wiley.com/doi/10.1002/sim.1536/abstract