Source code for cytoflow.utility.algorithms

#!/usr/bin/env python3.4
# coding: latin-1

# (c) Massachusetts Institute of Technology 2015-2018
# (c) Brian Teague 2018-2019
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 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
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <>.


Useful algorithms.

import numpy as np
from scipy import stats

[docs]def ci(data, func, which=95, boots=1000): """ Determine the confidence interval of a function applied to a data set by bootstrapping. Parameters ---------- data : pandas.DataFrame The data to resample. func : callable A function that is called on a resampled ``data`` which : int The percentile to use for the confidence interval boots : int (default = 1000): How many times to bootstrap Returns ------- (float, float) The confidence interval. """ boots = bootstrap(data, func = func, n_boot = boots) p = 50 - which / 2, 50 + which / 2 return tuple(percentiles(boots, p))
[docs]def percentiles(a, pcts, axis=None): """ Like scoreatpercentile but can take and return array of percentiles. from seaborn: Parameters ---------- a : array data pcts : sequence of percentile values percentile or percentiles to find score at axis : int or None if not None, computes scores over this axis Returns ------- scores: array array of scores at requested percentiles first dimension is length of object passed to ``pcts`` """ scores = [] try: n = len(pcts) except TypeError: pcts = [pcts] n = 0 for p in pcts: if axis is None: score = stats.scoreatpercentile(a.ravel(), p) else: score = np.apply_along_axis(stats.scoreatpercentile, axis, a, p) scores.append(score) scores = np.asarray(scores) if not n: scores = scores.squeeze() return scores
[docs]def bootstrap(*args, **kwargs): """ Resample one or more arrays with replacement and store aggregate values. Positional arguments are a sequence of arrays to bootstrap along the first axis and pass to a summary function. Parameters ---------- n_boot : int, default 10000 Number of iterations axis : int, default None Will pass axis to ``func`` as a keyword argument. units : array, default None Array of sampling unit IDs. When used the bootstrap resamples units and then observations within units instead of individual datapoints. smooth : bool, default False If True, performs a smoothed bootstrap (draws samples from a kernel destiny estimate); only works for one-dimensional inputs and cannot be used `units` is present. func : callable, default np.mean Function to call on the args that are passed in. random_seed : int | None, default None Seed for the random number generator; useful if you want reproducible resamples. Returns ------- array array of bootstrapped statistic values from seaborn: """ # Ensure list of arrays are same length if len(np.unique(list(map(len, args)))) > 1: raise ValueError("All input arrays must have the same length") n = len(args[0]) # Default keyword arguments n_boot = kwargs.get("n_boot", 10000) func = kwargs.get("func", np.mean) axis = kwargs.get("axis", None) units = kwargs.get("units", None) smooth = kwargs.get("smooth", False) random_seed = kwargs.get("random_seed", None) if axis is None: func_kwargs = dict() else: func_kwargs = dict(axis=axis) # Initialize the resampler rs = np.random.RandomState(random_seed) # Coerce to arrays args = list(map(np.asarray, args)) if units is not None: units = np.asarray(units) # Do the bootstrap if smooth: return _smooth_bootstrap(args, n_boot, func, func_kwargs) if units is not None: return _structured_bootstrap(args, n_boot, units, func, func_kwargs, rs) boot_dist = [] for i in range(int(n_boot)): resampler = rs.randint(0, n, n) sample = [a.take(resampler, axis=0) for a in args] boot_dist.append(func(*sample, **func_kwargs)) return np.array(boot_dist)
def _structured_bootstrap(args, n_boot, units, func, func_kwargs, rs): """Resample units instead of datapoints.""" unique_units = np.unique(units) n_units = len(unique_units) args = [[a[units == unit] for unit in unique_units] for a in args] boot_dist = [] for i in range(int(n_boot)): resampler = rs.randint(0, n_units, n_units) sample = [np.take(a, resampler, axis=0) for a in args] lengths = list(map(len, sample[0])) resampler = [rs.randint(0, n, n) for n in lengths] sample = [[c.take(r, axis=0) for c, r in zip(a, resampler)] for a in sample] sample = list(map(np.concatenate, sample)) boot_dist.append(func(*sample, **func_kwargs)) return np.array(boot_dist) def _smooth_bootstrap(args, n_boot, func, func_kwargs): """Bootstrap by resampling from a kernel density estimate.""" n = len(args[0]) boot_dist = [] kde = [stats.gaussian_kde(np.transpose(a)) for a in args] for i in range(int(n_boot)): sample = [a.resample(n).T for a in kde] boot_dist.append(func(*sample, **func_kwargs)) return np.array(boot_dist)