v0.18.0

0.18.0

• LogNormalFitter is a new univariate fitter you can use.
• WeibullFitter now correctly returns the confidence intervals (previously returned only NaNs)
• WeibullFitter.print_summary() displays p-values associated with its parameters not equal to 1.0 - previously this was (implicitly) comparing against 0, which is trivially always true (the parameters must be greater than 0)
• ExponentialFitter.print_summary() displays p-values associated with its parameters not equal to 1.0 - previously this was (implicitly) comparing against 0, which is trivially always true (the parameters must be greater than 0)
• ExponentialFitter.plot now displays the cumulative hazard, instead of the survival function. This is to make it easier to compare to WeibullFitter and LogNormalFitter
• Univariate fitters' cumulative_hazard_at_times, hazard_at_times, survival_function_at_times return pandas Series now (use to be numpy arrays)
• remove alpha keyword from all statistical functions. This was never being used.
• Gone are astericks and dots in print_summary functions that represent signficance thresholds.
• In models' summary (including print_summary), the log(p) term has changed to -log2(p). This is known as the s-value. See https://lesslikely.com/statistics/s-values/
• introduce new statistical tests between univariate datasets: survival_difference_at_fixed_point_in_time_test,...
• new warning message when Cox models detects possible non-unique solutions to maximum likelihood.
• Generally: clean up lifelines exception handling. Ex: catch LinAlgError: Matrix is singular. and report back to the user advice.