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# Statistical functions (`scipy.stats`)

This module contains a large number of probability distributions as well as a growing library of statistical functions.

Each included distribution is an instance of the class rv_continous: For each given name the following methods are available:

`rv_continuous`([momtype, a, b, xa, xb, xtol, ...]) | A generic continuous random variable class meant for subclassing.
`rv_continuous.pdf`(x, *args, **kwds) | Probability density function at x of the given RV.
`rv_continuous.logpdf`(x, *args, **kwds) | Log of the probability density function at x of the given RV.
`rv_continuous.cdf`(x, *args, **kwds) | Cumulative distribution function of the given RV.
`rv_continuous.logcdf`(x, *args, **kwds) | Log of the cumulative distribution function at x of the given RV.
`rv_continuous.sf`(x, *args, **kwds) | Survival function (1-cdf) at x of the given RV.
`rv_continuous.logsf`(x, *args, **kwds) | Log of the survival function of the given RV.
`rv_continuous.ppf`(q, *args, **kwds) | Percent point function (inverse of cdf) at q of the given RV.
`rv_continuous.isf`(q, *args, **kwds) | Inverse survival function at q of the given RV.
`rv_continuous.moment`(n, *args, **kwds) | n’th order non-central moment of distribution.
`rv_continuous.stats`(*args, **kwds) | Some statistics of the given RV
`rv_continuous.entropy`(*args, **kwds) | Differential entropy of the RV.
`rv_continuous.fit`(data, *args, **kwds) | Return MLEs for shape, location, and scale parameters from data.
`rv_continuous.expect`([func, args, loc, ...]) | Calculate expected value of a function with respect to the distribution

Calling the instance as a function returns a frozen pdf whose shape, location, and scale parameters are fixed.

Similarly, each discrete distribution is an instance of the class rv_discrete:

`rv_discrete`([a, b, name, badvalue, ...]) | A generic discrete random variable class meant for subclassing.
`rv_discrete.rvs`(*args, **kwargs) | Random variates of given type.
`rv_discrete.pmf`(k, *args, **kwds) | Probability mass function at k of the given RV.
`rv_discrete.logpmf`(k, *args, **kwds) | Log of the probability mass function at k of the given RV.
`rv_discrete.cdf`(k, *args, **kwds) | Cumulative distribution function of the given RV.
`rv_discrete.logcdf`(k, *args, **kwds) | Log of the cumulative distribution function at k of the given RV
`rv_discrete.sf`(k, *args, **kwds) | Survival function (1-cdf) at k of the given RV.
`rv_discrete.logsf`(k, *args, **kwds) | Log of the survival function of the given RV.
`rv_discrete.ppf`(q, *args, **kwds) | Percent point function (inverse of cdf) at q of the given RV
`rv_discrete.isf`(q, *args, **kwds) | Inverse survival function (1-sf) at q of the given RV.
`rv_discrete.stats`(*args, **kwds) | Some statistics of the given discrete RV.
`rv_discrete.moment`(n, *args, **kwds) | n’th non-central moment of the distribution
`rv_discrete.entropy`(*args, **kwds) |
`rv_discrete.expect`([func, args, loc, lb, ...]) | Calculate expected value of a function with respect to the distribution

## Continuous distributions

`alpha` | An alpha continuous random variable.
`anglit` | An anglit continuous random variable.
`arcsine` | An arcsine continuous random variable.
`beta` | A beta continuous random variable.
`betaprime` | A beta prima continuous random variable.
`bradford` | A Bradford continuous random variable.
`burr` | A Burr continuous random variable.
`cauchy` | A Cauchy continuous random variable.
`chi` | A chi continuous random variable.
`chi2` | A chi-squared continuous random variable.
`cosine` | A cosine continuous random variable.
`dgamma` | A double gamma continuous random variable.
`dweibull` | A double Weibull continuous random variable.
`erlang` | An Erlang continuous random variable.
`expon` | An exponential continuous random variable.
`exponweib` | An exponentiated Weibull continuous random variable.
`exponpow` | An exponential power continuous random variable.
`f` | An F continuous random variable.
`fatiguelife` | A fatigue-life (Birnbaum-Sanders) continuous random variable.
`fisk` | A Fisk continuous random variable.
`foldcauchy` | A folded Cauchy continuous random variable.
`foldnorm` | A folded normal continuous random variable.
`frechet_r` | A Frechet right (or Weibull minimum) continuous random variable.
`frechet_l` | A Frechet left (or Weibull maximum) continuous random variable.
`genlogistic` | A generalized logistic continuous random variable.
`genpareto` | A generalized Pareto continuous random variable.
`genexpon` | A generalized exponential continuous random variable.
`genextreme` | A generalized extreme value continuous random variable.
`gausshyper` | A Gauss hypergeometric continuous random variable.
`gamma` | A gamma continuous random variable.
`gengamma` | A generalized gamma continuous random variable.
`genhalflogistic` | A generalized half-logistic continuous random variable.
`gilbrat` | A Gilbrat continuous random variable.
`gompertz` | A Gompertz (or truncated Gumbel) continuous random variable.
`gumbel_r` | A right-skewed Gumbel continuous random variable.
`gumbel_l` | A left-skewed Gumbel continuous random variable.
`halfcauchy` | A Half-Cauchy continuous random variable.
`halflogistic` | A half-logistic continuous random variable.
`halfnorm` | A half-normal continuous random variable.
`hypsecant` | A hyperbolic secant continuous random variable.
`invgamma` | An inverted gamma continuous random variable.
`invgauss` | An inverse Gaussian continuous random variable.
`invweibull` | An inverted Weibull continuous random variable.
`johnsonsb` | A Johnson SB continuous random variable.
`johnsonsu` | A Johnson SU continuous random variable.
`ksone` | General Kolmogorov-Smirnov one-sided test.
`kstwobign` | Kolmogorov-Smirnov two-sided test for large N.
`laplace` | A Laplace continuous random variable.
`logistic` | A logistic continuous random variable.
`loggamma` | A log gamma continuous random variable.
`loglaplace` | A log-Laplace continuous random variable.
`lognorm` | A lognormal continuous random variable.
`lomax` | A Lomax (Pareto of the second kind) continuous random variable.
`maxwell` | A Maxwell continuous random variable.
`mielke` | A Mielke’s Beta-Kappa continuous random variable.
`nakagami` | A Nakagami continuous random variable.
`ncx2` | A non-central chi-squared continuous random variable.
`ncf` | A non-central F distribution continuous random variable.
`nct` | A non-central Student’s T continuous random variable.
`norm` | A normal continuous random variable.
`pareto` | A Pareto continuous random variable.
`pearson3` | A pearson type III continuous random variable.
`powerlaw` | A power-function continuous random variable.
`powerlognorm` | A power log-normal continuous random variable.
`powernorm` | A power normal continuous random variable.
`rdist` | An R-distributed continuous random variable.
`reciprocal` | A reciprocal continuous random variable.
`rayleigh` | A Rayleigh continuous random variable.
`rice` | A Rice continuous random variable.
`recipinvgauss` | A reciprocal inverse Gaussian continuous random variable.
`semicircular` | A semicircular continuous random variable.
`t` | A Student’s T continuous random variable.
`triang` | A triangular continuous random variable.
`truncexpon` | A truncated exponential continuous random variable.
`truncnorm` | A truncated normal continuous random variable.
`tukeylambda` | A Tukey-Lamdba continuous random variable.
`uniform` | A uniform continuous random variable.
`vonmises` | A Von Mises continuous random variable.
`wald` | A Wald continuous random variable.
`weibull_min` | A Frechet right (or Weibull minimum) continuous random variable.
`weibull_max` | A Frechet left (or Weibull maximum) continuous random variable.
`wrapcauchy` | A wrapped Cauchy continuous random variable.

## Discrete distributions

`bernoulli` | A Bernoulli discrete random variable.
`binom` | A binomial discrete random variable.
`boltzmann` | A Boltzmann (Truncated Discrete Exponential) random variable.
`dlaplace` | A Laplacian discrete random variable.
`geom` | A geometric discrete random variable.
`hypergeom` | A hypergeometric discrete random variable.
`logser` | A Logarithmic (Log-Series, Series) discrete random variable.
`nbinom` | A negative binomial discrete random variable.
`planck` | A Planck discrete exponential random variable.
`poisson` | A Poisson discrete random variable.
`randint` | A uniform discrete random variable.
`skellam` | A Skellam discrete random variable.
`zipf` | A Zipf discrete random variable.

## Statistical functions

Several of these functions have a similar version in scipy.stats.mstats which work for masked arrays.

`cmedian`(a[, numbins]) | Returns the computed median value of an array.
`describe`(a[, axis]) | Computes several descriptive statistics of the passed array.
`gmean`(a[, axis, dtype]) | Compute the geometric mean along the specified axis.
`hmean`(a[, axis, dtype]) | Calculates the harmonic mean along the specified axis.
`kurtosis`(a[, axis, fisher, bias]) | Computes the kurtosis (Fisher or Pearson) of a dataset.
`kurtosistest`(a[, axis]) | Tests whether a dataset has normal kurtosis
`mode`(a[, axis]) | Returns an array of the modal (most common) value in the passed array.
`moment`(a[, moment, axis]) | Calculates the nth moment about the mean for a sample.
`normaltest`(a[, axis]) | Tests whether a sample differs from a normal distribution.
`skew`(a[, axis, bias]) | Computes the skewness of a data set.
`skewtest`(a[, axis]) | Tests whether the skew is different from the normal distribution.
`tmean`(a[, limits, inclusive]) | Compute the trimmed mean
`tvar`(a[, limits, inclusive]) | Compute the trimmed variance
`tmin`(a[, lowerlimit, axis, inclusive]) | Compute the trimmed minimum
`tmax`(a, upperlimit[, axis, inclusive]) | Compute the trimmed maximum
`tstd`(a[, limits, inclusive]) | Compute the trimmed sample standard deviation
`tsem`(a[, limits, inclusive]) | Compute the trimmed standard error of the mean
`variation`(a[, axis]) | Computes the coefficient of variation, the ratio of the biased standard deviation to the mean.

`cumfreq`(a[, numbins, defaultreallimits, weights]) | Returns a cumulative frequency histogram, using the histogram function.
`histogram2`(a, bins) | Compute histogram using divisions in bins.
`histogram`(a[, numbins, defaultlimits, ...]) | Separates the range into several bins and returns the number of instances in each bin.
`itemfreq`(a) | Returns a 2D array of item frequencies.
`percentileofscore`(a, score[, kind]) | The percentile rank of a score relative to a list of scores.
`scoreatpercentile`(a, per[, limit, ...]) | Calculate the score at a given percentile of the input sequence.
`relfreq`(a[, numbins, defaultreallimits, weights]) | Returns a relative frequency histogram, using the histogram function.

`binned_statistic`(x, values[, statistic, ...]) | Compute a binned statistic for a set of data.
`binned_statistic_2d`(x, y, values[, ...]) | Compute a bidimensional binned statistic for a set of data.
`binned_statistic_dd`(sample, values[, ...]) | Compute a multidimensional binned statistic for a set of data.

`obrientransform`(*args) | Computes a transform on input data (any number of columns).
`signaltonoise`(a[, axis, ddof]) | The signal-to-noise ratio of the input data.
`bayes_mvs`(data[, alpha]) | Bayesian confidence intervals for the mean, var, and std.
`sem`(a[, axis, ddof]) | Calculates the standard error of the mean (or standard error of measurement) of the values in the input array.
`zmap`(scores, compare[, axis, ddof]) | Calculates the relative z-scores.
`zscore`(a[, axis, ddof]) | Calculates the z score of each value in the sample, relative to the sample mean and standard deviation.

`threshold`(a[, threshmin, threshmax, newval]) | Clip array to a given value.
`trimboth`(a, proportiontocut) | Slices off a proportion of items from both ends of an array.
`trim1`(a, proportiontocut[, tail]) | Slices off a proportion of items from ONE end of the passed array

`f_oneway`(*args) | Performs a 1-way ANOVA.
`pearsonr`(x, y) | Calculates a Pearson correlation coefficient and the p-value for testing
`spearmanr`(a[, b, axis]) | Calculates a Spearman rank-order correlation coefficient and the p-value
`pointbiserialr`(x, y) | Calculates a point biserial correlation coefficient and the associated p-value.
`kendalltau`(x, y[, initial_lexsort]) | Calculates Kendall’s tau, a correlation measure for ordinal data.
`linregress`(x[, y]) | Calculate a regression line

`ttest_1samp`(a, popmean[, axis]) | Calculates the T-test for the mean of ONE group of scores.
`ttest_ind`(a, b[, axis, equal_var]) | Calculates the T-test for the means of TWO INDEPENDENT samples of scores.
`ttest_rel`(a, b[, axis]) | Calculates the T-test on TWO RELATED samples of scores, a and b.
`kstest`(rvs, cdf[, args, N, alternative, mode]) | Perform the Kolmogorov-Smirnov test for goodness of fit.
`chisquare`(f_obs[, f_exp, ddof]) | Calculates a one-way chi square test.
`ks_2samp`(data1, data2) | Computes the Kolmogorov-Smirnof statistic on 2 samples.
`mannwhitneyu`(x, y[, use_continuity]) | Computes the Mann-Whitney rank test on samples x and y.
`tiecorrect`(rankvals) | Tie correction factor for ties in the Mann-Whitney U and
`rankdata`(a) | Assign ranks to the data in a, dealing with ties appropriately.
`ranksums`(x, y) | Compute the Wilcoxon rank-sum statistic for two samples.
`wilcoxon`(x[, y, zero_method]) | Calculate the Wilcoxon signed-rank test.
`kruskal`(*args) | Compute the Kruskal-Wallis H-test for independent samples
`friedmanchisquare`(*args) | Computes the Friedman test for repeated measurements

`ansari`(x, y) | Perform the Ansari-Bradley test for equal scale parameters
`bartlett`(*args) | Perform Bartlett’s test for equal variances
`levene`(*args, **kwds) | Perform Levene test for equal variances.
`shapiro`(x[, a, reta]) | Perform the Shapiro-Wilk test for normality.
`anderson`(x[, dist]) | Anderson-Darling test for data coming from a particular distribution
`binom_test`(x[, n, p]) | Perform a test that the probability of success is p.
`fligner`(*args, **kwds) | Perform Fligner’s test for equal variances.
`mood`(x, y) | Perform Mood’s test for equal scale parameters.
`oneway`(*args, **kwds) | Test for equal means in two or more samples from the normal distribution.

## Contingency table functions

`chi2_contingency`(observed[, correction]) | Chi-square test of independence of variables in a contingency table.
`contingency.expected_freq`(observed) | Compute the expected frequencies from a contingency table.
`contingency.margins`(a) | Return a list of the marginal sums of the array a.
`fisher_exact`(table[, alternative]) | Performs a Fisher exact test on a 2x2 contingency table.

## General linear model

`glm`(data, para) | Calculates a linear model fit ...

## Plot-tests

`ppcc_max`(x[, brack, dist]) | Returns the shape parameter that maximizes the probability plot correlation coefficient for the given data to a one-parameter family of distributions.
`ppcc_plot`(x, a, b[, dist, plot, N]) | Returns (shape, ppcc), and optionally plots shape vs.
`probplot`(x[, sparams, dist, fit, plot]) | Calculate quantiles for a probability plot of sample data against a specified theoretical distribution.

## Masked statistics functions

- Statistical functions for masked arrays (`scipy.stats.mstats`)
  - scipy.stats.mstats.argstoarray
  - scipy.stats.mstats.betai
  - scipy.stats.mstats.chisquare
  - scipy.stats.mstats.count_tied_groups
  - scipy.stats.mstats.describe
  - scipy.stats.mstats.f_oneway
  - scipy.stats.mstats.f_value_wilks_lambda
  - scipy.stats.mstats.find_repeats
  - scipy.stats.mstats.friedmanchisquare
  - scipy.stats.mstats.gmean
  - scipy.stats.mstats.hmean
  - scipy.stats.mstats.kendalltau
  - scipy.stats.mstats.kendalltau_seasonal
  - scipy.stats.mstats.kruskalwallis
  - scipy.stats.mstats.kruskalwallis
  - scipy.stats.mstats.ks_twosamp
  - scipy.stats.mstats.ks_twosamp
  - scipy.stats.mstats.kurtosis
  - scipy.stats.mstats.kurtosistest
  - scipy.stats.mstats.linregress
  - scipy.stats.mstats.mannwhitneyu
  - scipy.stats.mstats.plotting_positions
  - scipy.stats.mstats.mode
  - scipy.stats.mstats.moment
  - scipy.stats.mstats.mquantiles
  - scipy.stats.mstats.msign
  - scipy.stats.mstats.normaltest
  - scipy.stats.mstats.obrientransform
  - scipy.stats.mstats.pearsonr
  - scipy.stats.mstats.plotting_positions
  - scipy.stats.mstats.pointbiserialr
  - scipy.stats.mstats.rankdata
  - scipy.stats.mstats.scoreatpercentile
  - scipy.stats.mstats.sem
  - scipy.stats.mstats.signaltonoise
  - scipy.stats.mstats.skew
  - scipy.stats.mstats.skewtest
  - scipy.stats.mstats.spearmanr
  - scipy.stats.mstats.theilslopes
  - scipy.stats.mstats.threshold
  - scipy.stats.mstats.tmax
  - scipy.stats.mstats.tmean
  - scipy.stats.mstats.tmin
  - scipy.stats.mstats.trim
  - scipy.stats.mstats.trima
  - scipy.stats.mstats.trimboth
  - scipy.stats.mstats.trimmed_stde
  - scipy.stats.mstats.trimr
  - scipy.stats.mstats.trimtail
  - scipy.stats.mstats.tsem
  - scipy.stats.mstats.ttest_onesamp
  - scipy.stats.mstats.ttest_ind
  - scipy.stats.mstats.ttest_onesamp
  - scipy.stats.mstats.ttest_rel
  - scipy.stats.mstats.tvar
  - scipy.stats.mstats.variation
  - scipy.stats.mstats.winsorize
  - scipy.stats.mstats.zmap
  - scipy.stats.mstats.zscore

## Univariate and multivariate kernel density estimation (`scipy.stats.kde`)

`gaussian_kde`(dataset[, bw_method]) | Representation of a kernel-density estimate using Gaussian kernels.

For many more stat related functions install the software R and the interface package rpy.

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