scipy-yli/yli/survival.py

275 lines
8.5 KiB
Python

# scipy-yli: Helpful SciPy utilities and recipes
# Copyright © 2022–2023 Lee Yingtong Li (RunasSudo)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
import numpy as np
from scipy import stats
import statsmodels.api as sm
from .config import config
from .sig_tests import ChiSquaredResult
from .utils import Estimate, check_nan
def kaplanmeier(df, time, status, by=None, *, ci=True, transform_x=None, transform_y=None, nan_policy='warn'):
"""
Generate a Kaplan–Meier plot
Uses the Python *matplotlib* library.
:param df: Data to generate plot for
:type df: DataFrame
:param time: Column in *df* for the time to event (numeric or timedelta)
:type time: str
:param status: Column in *df* for the status variable (True/False or 1/0)
:type status: str
:param by: Column in *df* to stratify by (categorical)
:type by: str
:param ci: Whether to plot confidence intervals around the survival function
:type ci: bool
:param transform_x: Function to transform x axis by
:type transform_x: callable
:param transform_y: Function to transform y axis by
:type transform_y: callable
:param nan_policy: How to handle *nan* values (see :ref:`nan-handling`)
:type nan_policy: str
:rtype: (Figure, Axes)
"""
import matplotlib.pyplot as plt
# Check for/clean NaNs
if by:
df = check_nan(df[[time, status, by]], nan_policy)
else:
df = check_nan(df[[time, status]], nan_policy)
# Covert timedelta to numeric
df, time_units = survtime_to_numeric(df, time)
fig, ax = plt.subplots()
if by is not None:
# Group by independent variable
groups = df.groupby(by)
for group in groups.groups:
subset = groups.get_group(group)
handle = plot_survfunc_kaplanmeier(ax, subset[time], subset[status], ci, transform_x, transform_y)
handle.set_label('{} = {}'.format(by, group))
else:
# No grouping
plot_survfunc_kaplanmeier(ax, df[time], df[status], ci, transform_x, transform_y)
if time_units:
ax.set_xlabel('{} ({})'.format(time, time_units))
else:
ax.set_xlabel(time)
ax.set_ylabel('Survival probability ({:.0%} CI)'.format(1-config.alpha) if ci else 'Survival probability')
ax.set_xlim(left=0)
ax.set_ylim(0, 1)
ax.legend()
return fig, ax
def plot_survfunc_kaplanmeier(ax, time, status, ci, transform_x=None, transform_y=None):
# Estimate the survival function
sf = sm.SurvfuncRight(time, status)
# Draw straight lines
xpoints = sf.surv_times.repeat(2)[1:]
ypoints = sf.surv_prob.repeat(2)[:-1]
handle = ax.plot(xpoints, ypoints)[0]
if transform_x:
xpoints = transform_x(xpoints)
if transform_y:
ypoints = transform_y(ypoints)
if ci:
zstar = -stats.norm.ppf(config.alpha/2)
# Get confidence intervals
ci0 = sf.surv_prob - zstar * sf.surv_prob_se
ci1 = sf.surv_prob + zstar * sf.surv_prob_se
# Plot confidence intervals
ypoints0 = ci0.repeat(2)[:-1]
ypoints1 = ci1.repeat(2)[:-1]
if transform_y:
ypoints0 = transform_y(ypoints0)
ypoints1 = transform_y(ypoints1)
ax.fill_between(xpoints, ypoints0, ypoints1, alpha=0.3, label='_')
return handle
def turnbull(df, time_left, time_right, by=None, *, transform_x=None, transform_y=None, nan_policy='warn'):
"""
Generate a Turnbull estimator plot, which extends the Kaplan–Meier estimator to interval-censored observations
The intervals are assumed to be half-open intervals, (*left*, *right*]. *right* == *np.inf* implies the event was right-censored. Unlike :func:`yli.kaplanmeier`, times must be given as numeric dtypes and not as pandas timedelta.
For ease of interpretation, the survival function is drawn as a step function at the midpoint of the estimate on each interval.
Uses the Python *lifelines* and *matplotlib* libraries.
:param df: Data to generate plot for
:type df: DataFrame
:param time_left: Column in *df* for the time to event, left interval endpoint (numeric)
:type time_left: str
:param time_right: Column in *df* for the time to event, right interval endpoint (numeric)
:type time_right: str
:param by: Column in *df* to stratify by (categorical)
:type by: str
:param transform_x: Function to transform x axis by
:type transform_x: callable
:param transform_y: Function to transform y axis by
:type transform_y: callable
:param nan_policy: How to handle *nan* values (see :ref:`nan-handling`)
:type nan_policy: str
:rtype: (Figure, Axes)
"""
import matplotlib.pyplot as plt
# Check for/clean NaNs
if by:
df = check_nan(df[[time_left, time_right, by]], nan_policy)
else:
df = check_nan(df[[time_left, time_right]], nan_policy)
fig, ax = plt.subplots()
if by is not None:
# Group by independent variable
groups = df.groupby(by)
for group in groups.groups:
subset = groups.get_group(group)
handle = plot_survfunc_turnbull(ax, subset[time_left], subset[time_right], transform_x, transform_y)
handle.set_label('{} = {}'.format(by, group))
else:
# No grouping
plot_survfunc_turnbull(ax, df[time_left], df[time_right], transform_x, transform_y)
ax.set_xlabel('Analysis time')
ax.set_ylabel('Survival probability')
ax.set_xlim(left=0)
ax.set_ylim(0, 1)
ax.legend()
return fig, ax
def plot_survfunc_turnbull(ax, time_left, time_right, transform_x=None, transform_y=None):
import lifelines
EPSILON = 1e-10
# TODO: Support left == right => failure was exactly observed
followup_left = time_left + EPSILON # Add epsilon to make interval half-open
followup_right = time_right
# Estimate the survival function
sf = lifelines.KaplanMeierFitter().fit_interval_censoring(followup_left, followup_right)
# Draw straight lines
xpoints = sf.survival_function_.index.to_numpy().repeat(2)[:-1]
med = (sf.survival_function_['NPMLE_estimate_upper'] + sf.survival_function_['NPMLE_estimate_lower']) / 2
ypoints = med.to_numpy().repeat(2)[1:]
if transform_x:
xpoints = transform_x(xpoints)
if transform_y:
ypoints = transform_y(ypoints)
handle = ax.plot(xpoints, ypoints)[0]
return handle
def survtime_to_numeric(df, time):
"""
Convert pandas timedelta dtype to float64, auto-detecting the best time unit to display
:param df: Data to check for pandas timedelta dtype
:type df: DataFrame
:param time: Column to check for pandas timedelta dtype
:type df: DataFrame
:return: (*df*, *time_units*)
* **df** (*DataFrame*) – Data with pandas timedelta dtypes converted, which is *not* copied
* **time_units** (*str*) – Human-readable description of the time unit, or *None* if not converted
"""
if df[time].dtype == '<m8[ns]':
df[time] = df[time].dt.total_seconds()
# Auto-detect best time units
if df[time].max() > 365.24*24*60*60:
df[time] = df[time] / (365.24*24*60*60)
time_units = 'years'
elif df[time].max() > 7*24*60*60 / 12:
df[time] = df[time] / (7*24*60*60)
time_units = 'weeks'
elif df[time].max() > 24*60*60:
df[time] = df[time] / (24*60*60)
time_units = 'days'
elif df[time].max() > 60*60:
df[time] = df[time] / (60*60)
time_units = 'hours'
elif df[time].max() > 60:
df[time] = df[time] / 60
time_units = 'minutes'
else:
time_units = 'seconds'
return df, time_units
else:
return df, None
def logrank(df, time, status, by, nan_policy='warn'):
"""
Perform the log-rank test for equality of survival functions
:param df: Data to perform the test on
:type df: DataFrame
:param time: Column in *df* for the time to event (numeric or timedelta)
:type time: str
:param status: Column in *df* for the status variable (True/False or 1/0)
:type status: str
:param by: Column in *df* to stratify by (categorical)
:type by: str
:param nan_policy: How to handle *nan* values (see :ref:`nan-handling`)
:type nan_policy: str
:rtype: :class:`yli.sig_tests.ChiSquaredResult`
"""
# TODO: Example
# Check for/clean NaNs
df = check_nan(df[[time, status, by]], nan_policy)
if df[time].dtype == '<m8[ns]':
df[time] = df[time].dt.total_seconds()
statistic, pvalue = sm.duration.survdiff(df[time], df[status], df[by])
return ChiSquaredResult(statistic=statistic, dof=1, pvalue=pvalue)