### Changelogs



####0.4.2

 - Massive speed improvements to CoxPHFitter. 
 - Additional prediction method: `predict_percentile` is available on CoxPHFitter and AalenAdditiveFitter. Given a percentile, p, this function returns the value t such that *S(t | x) = p*. It is a generalization of `predict_median`. 
 - Additional kwargs in `k_fold_cross_validation` that will accept different prediction methods (default is `predict_median`). 
- Bug fix in CoxPHFitter `predict_expectation` function. 
- Correct spelling mistake in newton-rhapson algorithm.
- `datasets` now contains functions for generating the respective datasets, ex: `generate_waltons_dataset`.
- Bumping up the number of samples in statistical tests to prevent them from failing so often (this a stop-gap)
- pep8 everything

####0.4.1.1

- Ability to specify default printing in statsitical tests with the `suppress_print` keyword argument (default False).
- For the multivariate log rank test, the inverse step has been replaced with the generalized inverse. This seems to be what other packages use.
- Adding more robust cross validation scheme based on issue #67.
- fixing `regression_dataset` in `datasets`.
 

####0.4.1

 - `CoxFitter` is now known as `CoxPHFitter`
 - refactoring some tests that used redundant data from `lifelines.datasets`. 
 - Adding cross validation: in `utils` is a new `k_fold_cross_validation` for model selection in regression problems.
 - Change CoxPHFitter's fit method's `display_output` to `False`.
 - fixing bug in CoxPHFitter's `_compute_baseline_hazard` that errored when sending Series objects to
   `survival_table_from_events`.
 - CoxPHFitter's `fit` now looks to columns with too low variance, and halts NR algorithm if a NaN is found.
 - Adding a Changelog.
 - more sanitizing for the statistical tests =)

####0.4.0

 - `CoxFitter` implements Cox Proportional Hazards model in lifelines. 
 - lifelines moves the wheels distributions.
 - tests in the `statistics` module now prints the summary (and still return the regular values)
 - new `BaseFitter` class is inherited from all fitters. 