Contents

module Statsample
    module Anova
        # One Way Anova
        # Example:
        #   v1=[2,3,4,5,6].to_vector(:scale)
        #   v2=[3,3,4,5,6].to_vector(:scale)
        #   v3=[5,3,1,5,6].to_vector(:scale)
        #   anova=Statsample::Anova::OneWay.new([v1,v2,v3])
        #   puts anova.f
        #   puts anova.significance
        class OneWay
        def initialize(vectors)
            @vectors=vectors
        end
        # Total sum
        def sum
            @vectors.inject(0){|a,v| a+v.sum}
        end
	# Total mean
	def mean
            sum.quo(n)
        end
        # Total sum of squares
        def sst
            m=mean.to_f
            @vectors.inject(0) {|total,vector|
                total+vector.sum_of_squares(m)
            }
        end
        # Sum of squares within groups
        def sswg
            @vectors.inject(0) {|total,vector|
                total+vector.sum_of_squares
            }
        end
        # Sum of squares between groups
        def ssbg
            m=mean
            @vectors.inject(0) {|total,vector|
                total+(vector.mean-m).square*vector.size
            }
        end
        # Degrees of freedom within groups
        def df_wg
            @vectors.inject(0) {|a,v| a+(v.size-1)}
        end
        # Degrees of freedom between groups 
        def df_bg
            @vectors.size-1
        end
        # Total Degrees of freedom
        def df_total
            n-1
        end
        # Total number of cases
        def n
            @vectors.inject(0){|a,v| a+v.size}
        end
        # Fisher
        def f
            k=@vectors.size
            (ssbg*(n-k)) / (sswg*(k-1))
        end
        # Significance of Fisher
        def significance
            1.0-Distribution::F.cdf(f,df_bg,df_wg)
        end
    end
    end
end

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
statsample-0.5.0	lib/statsample/anova.rb
statsample-0.4.1	lib/statsample/anova.rb
statsample-0.4.0	lib/statsample/anova.rb