Covariance

• New method for calculating covariance: Stat::covariance()

Frequency Table

• frequencyTable()
• frequencyTableBySize()
• code refactoring and documenting some functions by Artem Trokhymchuk @trokhymchuk thanks for the PR #2
• add tests for Math class

Quantiles

• quantiles()
• firstQuartile()
• thirdQuartile()

Geometric and Harmonic Mean

• geometricMean(): geometric mean
• harmonicMean(): harmonic mean and weighted harmonic mean

Standard Deviation and Variance

• pstdev(): Population standard deviation
• stdev(): Sample standard deviation
• pvariance(): variance for a population
• variance(): variance for a sample

Freq and Stat classes

• Create Freq class with static method for managing frequencies table
• Create Stat class with static methods for basci statistic functions like: mean, mode, median, multimode...
• Refactor Statistics class in order to use logic provided by Freq and Stat class
• Create ArrUtil with some helpers/functions to manage arrays
• Add CICD test for PHP 8.1

Initial release

Initial release with:

• getMean()
• getCount()
• getMedian()
• getLowerPercentile()
• getHigherPercentile()
• getMode()
• getFrequencies(): a frequency is the number of times a value of the data occurs;
• getRelativeFrequencies(): a relative frequency is the ratio (fraction or proportion) of the number of times a value of the data occurs in the set of all outcomes to the total number of outcomes;
• getCumulativeFrequences(): is the accumulation of the previous relative frequencies.;
• getCumulativeRelativeFrequencies(): is the accumulation of the previous relative ratio.