statsmodels.stats.weightstats.DescrStatsW¶

class
statsmodels.stats.weightstats.
DescrStatsW
(data, weights=None, ddof=0)[source]¶ descriptive statistics and tests with weights for case weights
Assumes that the data is 1d or 2d with (nobs, nvars) observations in rows, variables in columns, and that the same weight applies to each column.
If degrees of freedom correction is used, then weights should add up to the number of observations. ttest also assumes that the sum of weights corresponds to the sample size.
This is essentially the same as replicating each observations by its weight, if the weights are integers, often called case or frequency weights.
Parameters: data : array_like, 1D or 2D
dataset
weights : None or 1D ndarray
weights for each observation, with same length as zero axis of data
ddof : int
default ddof=0, degrees of freedom correction used for second moments, var, std, cov, corrcoef. However, statistical tests are independent of ddof, based on the standard formulas.
Examples
Note: I don’t know the seed for the following, so the numbers will differ
>>> x1_2d = 1.0 + np.random.randn(20, 3) >>> w1 = np.random.randint(1,4, 20) >>> d1 = DescrStatsW(x1_2d, weights=w1) >>> d1.mean array([ 1.42739844, 1.23174284, 1.083753 ]) >>> d1.var array([ 0.94855633, 0.52074626, 1.12309325]) >>> d1.std_mean array([ 0.14682676, 0.10878944, 0.15976497])
>>> tstat, pval, df = d1.ttest_mean(0) >>> tstat; pval; df array([ 9.72165021, 11.32226471, 6.78342055]) array([ 1.58414212e12, 1.26536887e14, 2.37623126e08]) 44.0
>>> tstat, pval, df = d1.ttest_mean([0, 1, 1]) >>> tstat; pval; df array([ 9.72165021, 2.13019609, 0.52422632]) array([ 1.58414212e12, 3.87842808e02, 6.02752170e01]) 44.0
#if weiqhts are integers, then asrepeats can be used
>>> x1r = d1.asrepeats() >>> x1r.shape ... >>> stats.ttest_1samp(x1r, [0, 1, 1]) ...
Methods
asrepeats
()get array that has repeats given by floor(weights) corrcoef
()weighted correlation with default ddof cov
()weighted covariance of data if data is 2 dimensional demeaned
()data with weighted mean subtracted get_compare
(other[, weights])return an instance of CompareMeans with self and other mean
()weighted mean of data nobs
()alias for number of observations/cases, equal to sum of weights std
()standard deviation with default degrees of freedom correction std_ddof
([ddof])standard deviation of data with given ddof std_mean
()standard deviation of weighted mean sum
()weighted sum of data sum_weights
()sumsquares
()weighted sum of squares of demeaned data tconfint_mean
([alpha, alternative])twosided confidence interval for weighted mean of data ttest_mean
([value, alternative])ttest of Null hypothesis that mean is equal to value. ttost_mean
(low, upp)test of (non)equivalence of one sample var
()variance with default degrees of freedom correction var_ddof
([ddof])variance of data given ddof zconfint_mean
([alpha, alternative])twosided confidence interval for weighted mean of data ztest_mean
([value, alternative])ztest of Null hypothesis that mean is equal to value. ztost_mean
(low, upp)test of (non)equivalence of one sample, based on ztest