Calculate Schoenfeld or Event Proportion based event numbers from power
power2events(power, HR, ratio = 1, alpha1 = 0.025)
Desired power (decimal).
Hazard Ratio. Values below 1 indicate a benefit to the active arm vs control.
Randomisation ratio (Schoenfeld), or event ratio (event proportion method). Default=1.
1-sided alpha. Default=0.025.
Required event number