• adding plot_covariate_groups to CoxPHFitter to visualize what happens to survival as we vary a covariate, all else being equal.
• utils functions like qth_survival_times and median_survival_times now return the transpose of the DataFrame compared to previous version of lifelines. The reason for this is that we often treat survival curves as columns in DataFrames, and functions of the survival curve as index (ex: KaplanMeierFitter.survival_function_ returns a survival curve at time t).
• KaplanMeierFitter.fit and NelsonAalenFitter.fit accept a weights vector that can be used for pre-aggregated datasets. See this issue.
• Convergence errors now return a custom ConvergenceWarning instead of a RuntimeWarning
• New checks for complete separation in the dataset for regressions.