# encoding: utf-8
require 'spec_helper'

describe Rstat do
  describe ".sum" do
    it "calculates the sum of an array" do
      [1, 2, 3, 4, 5, 6].sum.should be(21)
    end
  end

  describe ".product" do
    it "calculates the product of an array" do
      [1, 2, 3, 4, 5, 6].product.should be(720)
    end
  end

  context "Location" do
    describe ".mean" do
        it "calculates the mean of an array" do
          [1, 2, 3, 4, 5].mean.should be_within(0.0001).of(3.0000)
        end
    end

    describe ".geometric_mean" do
      it "calculates the geometric mean of an array" do
        [1, 2, 3, 4, 5].geometric_mean.should be_within(0.0001).of(2.6052)
      end

      it "calculates the geometric mean of an array with a zero element" do
        [0, 2, 3, 4, 5].geometric_mean.should eql(0.0)
      end

      it "calculates the geometric mean of an array with a negative element" do
        [-1, 2, 3, 4, 5].geometric_mean.real?.should be_false
      end
    end

    describe ".harmonic mean" do
      it "calculates the harmonic mean of an array" do
        [1, 2, 3, 4, 5].harmonic_mean.should be_within(0.0001).of(2.1897)
      end
    end

    describe ".power_mean" do
      it "power_mean(2) should equal quadratic_mean" do
        p = [1, 2, 3, 4, 5].power_mean(2)
        q = [1, 2, 3, 4, 5].quadratic_mean

        p.should eql(q)
      end
    end

    it "AM > GM > HM" do
      a = [1, 2, 3, 4, 5]
      am = a.arithmetric_mean
      gm = a.geometric_mean
      hm = a.harmonic_mean

      am.should be > gm
      gm.should be > hm
    end

    describe ".median" do
      it "calculates the median of an array with an odd number of elements" do
        [2, 3, 5, 1, 4].median.should eql(3)
      end

      it "calculates the median of an array with an even number of elements" do
        [2, 3, 5, 1, 4, 6].median.should eql(3.5)
      end
    end

    describe ".mode" do
      it "calculates the mode of an empty array" do
        [].mode.should eql([])
      end

      it "calculates the mode of an array with one element" do
        [100].mode.should eql([100])
      end

      it "calculates the mode of an unimodal array" do
        [1, 1, 1, 2, 3, 4, 5, 5, 6].mode.should eql([1])
      end

      it "calculates the mode of a bimodal array" do
        [44, 45, 46, 44, 46, 50].mode.should eql([44, 46])
      end
    end
  end

  context "Dispersion" do
    describe ".range" do
      it "finds the range of an array" do
        [0, 34, 656, 400, 1000].range.should be(1000)
      end
    end

    describe ".standard_deviation" do
      it "calculates the standard deviation of an array" do
        [1, 2, 3, 4, 5, 6].standard_deviation.should be_within(0.00001).of(1.70783)
      end
    end

    describe ".coefficient_of_variation" do
      it "calculates the coefficient of variation of an array" do
        [1, 2, 3, 4, 5, 6].coefficient_of_variation.should be_within(0.00001).of(0.48795)
      end
    end

    describe ".percentile" do
      it "finds the 30th percentile of an array" do
        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].percentile(30).should be(3)
      end

      it "finds the 50th percentile of an array" do
        [1, 2, 3, 4, 5].percentile(50).should be(3)
      end

      it "finds the 10th percentile of an array" do
        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17].percentile(10).should be(2)
      end
    end

    describe ".interquartile_range" do
      it "finds the interquartile range of an array" do
        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].interquartile_range.should be(5)
      end
    end
  end

  context "Shape" do
    describe ".central_moment" do
      it "calculates the 0th central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].central_moment(0).should be_within(0.00001).of(1.0)
      end

      it "calculates the 1st central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].central_moment(1).should be_within(0.00001).of(0.0)
      end

      it "calculates the 2nd central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].central_moment(2).should be_within(0.00001).of(3459.44000)
      end

      it "calculates the 3rd central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].central_moment(3).should be_within(0.00001).of(321046.00800)
      end

      it "calculates the 4th central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].central_moment(4).should be_within(0.00001).of(56245095.69920)
      end
    end

    describe ".raw_moment" do
      it "calculates the 0th central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].raw_moment(0).should be_within(0.00001).of(1.0)
      end

      it "calculates the 1st central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].raw_moment(1).should be_within(0.00001).of([2, 43, 5, 65, 56, 7, 85, 3, -1, 199].mean)
      end

      it "calculates the 2nd central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].raw_moment(2).should be_within(0.00001).of(5612.40000)
      end

      it "calculates the 3rd central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].raw_moment(3).should be_within(0.00001).of(902497.40000)
      end

      it "calculates the 4th central moment of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].raw_moment(4).should be_within(0.00001).of(165154687.20000)
      end
    end

    describe ".variance" do
      it "calculates the variance of an array" do
        [1, 2, 3, 4, 5, 6].variance.should be_within(0.00001).of(2.91667)
      end
    end

    describe ".skewness" do
      it "finds the skewness of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].skewness.should be_within(0.00001).of(1.57782)
      end
    end

    describe ".kurtosis" do
      it "finds the kurtosis of an array" do
        [2, 43, 5, 65, 56, 7, 85, 3, -1, 199].kurtosis.should be_within(0.00001).of(1.69973)
      end
    end
  end

  context "Count Data" do
    describe ".index_of_dispersion" do
      it "finds the index of dispersion of an array" do
        [1, 2, 3, 4, 5, 6].index_of_dispersion.should be_within(0.00001).of(0.83333)
      end
    end
  end
end