LogLogisticFitter¶
-
class
lifelines.fitters.log_logistic_fitter.
LogLogisticFitter
(*args, **kwargs)¶ Bases:
lifelines.fitters.KnownModelParametricUnivariateFitter
This class implements a Log-Logistic model for univariate data. The model has parameterized form:
\[S(t) = \left(1 + \left(\frac{t}{\alpha}\right)^{\beta}\right)^{-1}, \alpha > 0, \beta > 0,\]The \(\alpha\) (scale) parameter has an interpretation as being equal to the median lifetime of the population. The \(\beta\) parameter influences the shape of the hazard. See figure below:
The hazard rate is:
\[h(t) = \frac{\left(\frac{\beta}{\alpha}\right)\left(\frac{t}{\alpha}\right) ^ {\beta-1}}{\left(1 + \left(\frac{t}{\alpha}\right)^{\beta}\right)}\]and the cumulative hazard is:
\[H(t) = \log\left(\left(\frac{t}{\alpha}\right) ^ {\beta} + 1\right)\]After calling the
.fit
method, you have access to properties like:cumulative_hazard_
,plot
,survival_function_
,alpha_
andbeta_
. A summary of the fit is available with the method ‘print_summary()’Parameters: alpha (float, optional (default=0.05)) – the level in the confidence intervals. Examples
from lifelines import LogLogisticFitter from lifelines.datasets import load_waltons waltons = load_waltons() llf = LogLogisticFitter() llf.fit(waltons['T'], waltons['E']) llf.plot() print(llf.alpha_)
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cumulative_hazard_
¶ The estimated cumulative hazard (with custom timeline if provided)
Type: DataFrame
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hazard_
¶ The estimated hazard (with custom timeline if provided)
Type: DataFrame
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survival_function_
¶ The estimated survival function (with custom timeline if provided)
Type: DataFrame
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cumulative_density_
¶ The estimated cumulative density function (with custom timeline if provided)
Type: DataFrame
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density_
¶ The estimated density function (PDF) (with custom timeline if provided)
Type: DataFrame
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variance_matrix_
¶ The variance matrix of the coefficients
Type: DataFrame
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median_survival_time_
¶ The median time to event
Type: float
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alpha_
¶ The fitted parameter in the model
Type: float
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beta_
¶ The fitted parameter in the model
Type: float
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durations
¶ The durations provided
Type: array
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event_observed
¶ The event_observed variable provided
Type: array
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timeline
¶ The time line to use for plotting and indexing
Type: array
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entry
¶ The entry array provided, or None
Type: array or None
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AIC_
¶
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BIC_
¶
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conditional_time_to_event_
¶ Return a DataFrame, with index equal to survival_function_, that estimates the median duration remaining until the death event, given survival up until time t. For example, if an individual exists until age 1, their expected life remaining given they lived to time 1 might be 9 years.
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confidence_interval_
¶ The confidence interval of the cumulative hazard. This is an alias for
confidence_interval_cumulative_hazard_
.
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confidence_interval_cumulative_density_
¶ The lower and upper confidence intervals for the cumulative density
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confidence_interval_cumulative_hazard_
¶ The confidence interval of the cumulative hazard. This is an alias for
confidence_interval_
.
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confidence_interval_density_
¶ The confidence interval of the hazard.
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confidence_interval_hazard_
¶ The confidence interval of the hazard.
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confidence_interval_survival_function_
¶ The lower and upper confidence intervals for the survival function
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cumulative_density_at_times
(times, label: Optional[str] = None) → pandas.core.series.Series¶ Return a Pandas series of the predicted cumulative density function (1-survival function) at specific times.
Parameters: - times (iterable or float) – values to return the survival function at.
- label (string, optional) – Rename the series returned. Useful for plotting.
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cumulative_hazard_at_times
(times, label: Optional[str] = None) → pandas.core.series.Series¶ Return a Pandas series of the predicted cumulative hazard value at specific times.
Parameters: - times (iterable or float) – values to return the cumulative hazard at.
- label (string, optional) – Rename the series returned. Useful for plotting.
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density_at_times
(times, label=None) → pandas.core.series.Series¶ Return a Pandas series of the predicted probability density function, dCDF/dt, at specific times.
Parameters: - times (iterable or float) – values to return the survival function at.
- label (string, optional) – Rename the series returned. Useful for plotting.
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divide
(other) → pandas.core.frame.DataFrame¶ Divide self’s survival function from another model’s survival function.
Parameters: other (same object as self)
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event_table
¶
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fit
(durations, event_observed=None, timeline=None, label=None, alpha=None, ci_labels=None, show_progress=False, entry=None, weights=None, initial_point=None, fit_options: Optional[dict] = None) → ParametricUnivariateFitter¶ Parameters: - durations (an array, or pd.Series) – length n, duration subject was observed for
- event_observed (numpy array or pd.Series, optional) – length n, True if the the death was observed, False if the event was lost (right-censored). Defaults all True if event_observed==None
- timeline (list, optional) – return the estimate at the values in timeline (positively increasing)
- label (string, optional) – a string to name the column of the estimate.
- alpha (float, optional) – the alpha value in the confidence intervals. Overrides the initializing alpha for this call to fit only.
- ci_labels (list, optional) – add custom column names to the generated confidence intervals as a length-2 list: [<lower-bound name>, <upper-bound name>]. Default: <label>_lower_<alpha>
- show_progress (bool, optional) – since this is an iterative fitting algorithm, switching this to True will display some iteration details.
- entry (an array, or pd.Series, of length n) – relative time when a subject entered the study. This is useful for left-truncated (not left-censored) observations. If None, all members of the population entered study when they were “born”: time zero.
- weights (an array, or pd.Series, of length n) – integer weights per observation
- initial_point ((d,) numpy array, optional) – initialize the starting point of the iterative algorithm. Default is the zero vector.
- fit_options (dict, optional) – pass kwargs into the underlying minimization algorithm, like
tol
, etc.
Returns: self with new properties like
cumulative_hazard_
,survival_function_
Return type: self
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fit_interval_censoring
(lower_bound, upper_bound, event_observed=None, timeline=None, label=None, alpha=None, ci_labels=None, show_progress=False, entry=None, weights=None, initial_point=None, fit_options: Optional[dict] = None) → ParametricUnivariateFitter¶ Fit the model to an interval censored dataset.
Parameters: - lower_bound (an array, or pd.Series) – length n, the start of the period the subject experienced the event in.
- upper_bound (an array, or pd.Series) – length n, the end of the period the subject experienced the event in. If the value is equal to the corresponding value in lower_bound, then the individual’s event was observed (not censored).
- event_observed (numpy array or pd.Series, optional) – length n, if left optional, infer from
lower_bound
andupper_cound
(if lower_bound==upper_bound then event observed, if lower_bound < upper_bound, then event censored) - timeline (list, optional) – return the estimate at the values in timeline (positively increasing)
- label (string, optional) – a string to name the column of the estimate.
- alpha (float, optional) – the alpha value in the confidence intervals. Overrides the initializing alpha for this call to fit only.
- ci_labels (list, optional) – add custom column names to the generated confidence intervals as a length-2 list: [<lower-bound name>, <upper-bound name>]. Default: <label>_lower_<alpha>
- show_progress (bool, optional) – since this is an iterative fitting algorithm, switching this to True will display some iteration details.
- entry (an array, or pd.Series, of length n) – relative time when a subject entered the study. This is useful for left-truncated (not left-censored) observations. If None, all members of the population entered study when they were “born”: time zero.
- weights (an array, or pd.Series, of length n) – integer weights per observation
- initial_point ((d,) numpy array, optional) – initialize the starting point of the iterative algorithm. Default is the zero vector.
- fit_options (dict, optional) – pass kwargs into the underlying minimization algorithm, like
tol
, etc.
Returns: self with new properties like
cumulative_hazard_
,survival_function_
Return type: self
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fit_left_censoring
(durations, event_observed=None, timeline=None, label=None, alpha=None, ci_labels=None, show_progress=False, entry=None, weights=None, initial_point=None, fit_options: Optional[dict] = None) → ParametricUnivariateFitter¶ Fit the model to a left-censored dataset
Parameters: - durations (an array, or pd.Series) – length n, duration subject was observed for
- event_observed (numpy array or pd.Series, optional) – length n, True if the the death was observed, False if the event was lost (right-censored). Defaults all True if event_observed==None
- timeline (list, optional) – return the estimate at the values in timeline (positively increasing)
- label (string, optional) – a string to name the column of the estimate.
- alpha (float, optional) – the alpha value in the confidence intervals. Overrides the initializing alpha for this call to fit only.
- ci_labels (list, optional) – add custom column names to the generated confidence intervals as a length-2 list: [<lower-bound name>, <upper-bound name>]. Default: <label>_lower_<alpha>
- show_progress (bool, optional) – since this is an iterative fitting algorithm, switching this to True will display some iteration details.
- entry (an array, or pd.Series, of length n) – relative time when a subject entered the study. This is useful for left-truncated (not left-censored) observations. If None, all members of the population entered study when they were “born”: time zero.
- weights (an array, or pd.Series, of length n) – integer weights per observation
- initial_point ((d,) numpy array, optional) – initialize the starting point of the iterative algorithm. Default is the zero vector.
- fit_options (dict, optional) – pass kwargs into the underlying minimization algorithm, like
tol
, etc.
Returns: Return type: self with new properties like
cumulative_hazard_
,survival_function_
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hazard_at_times
(times, label: Optional[str] = None) → pandas.core.series.Series¶ Return a Pandas series of the predicted hazard at specific times.
Parameters: - times (iterable or float) – values to return the hazard at.
- label (string, optional) – Rename the series returned. Useful for plotting.
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label
¶
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median_survival_time_
Return the unique time point, t, such that S(t) = 0.5. This is the “half-life” of the population, and a robust summary statistic for the population, if it exists.
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params_
¶
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percentile
(p)¶ Return the unique time point, t, such that S(t) = p.
Parameters: p (float)
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plot
(**kwargs)¶ Produce a pretty-plot of the estimate.
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plot_cumulative_density
(**kwargs)¶
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plot_cumulative_hazard
(**kwargs)¶
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plot_density
(**kwargs)¶
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plot_hazard
(**kwargs)¶
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plot_survival_function
(**kwargs)¶
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predict
(times: Union[Iterable[float], float], interpolate=False) → pandas.core.series.Series¶ Predict the fitter at certain point in time. Uses a linear interpolation if points in time are not in the index.
Parameters: - times (scalar, or array) – a scalar or an array of times to predict the value of {0} at.
- interpolate (bool, optional (default=False)) – for methods that produce a stepwise solution (Kaplan-Meier, Nelson-Aalen, etc), turning this to True will use an linear interpolation method to provide a more “smooth” answer.
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print_summary
(decimals=2, style=None, columns=None, **kwargs)¶ Print summary statistics describing the fit, the coefficients, and the error bounds.
Parameters: - decimals (int, optional (default=2)) – specify the number of decimal places to show
- style (string) – {html, ascii, latex}
- columns – only display a subset of
summary
columns. Default all. - kwargs – print additional metadata in the output (useful to provide model names, dataset names, etc.) when comparing multiple outputs.
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subtract
(other) → pandas.core.frame.DataFrame¶ Subtract self’s survival function from another model’s survival function.
Parameters: other (same object as self)
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summary
¶ Summary statistics describing the fit.
See also
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survival_function_at_times
(times, label: Optional[str] = None) → pandas.core.series.Series¶ Return a Pandas series of the predicted survival value at specific times.
Parameters: - times (iterable or float) – values to return the survival function at.
- label (string, optional) – Rename the series returned. Useful for plotting.
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