Continuous Uniform distribution - estebanz01/ruby-statistics GitHub Wiki

Instance methods

Cumulative function

It calculates the probability P(x <= X) for an specified X, based on the left/right values specified at initialization time. If the specified value X <= left, then the result is zero. If the specified value X >= right, it returns one.

[78] pry(main)> Distribution::Uniform.new(3,4)
=> #<Statistics::Distribution::Uniform:0x00000000019d4fd0 @left=3.0, @right=4.0>
[79] pry(main)> Distribution::Uniform.new(3,4).cumulative_function(2)
=> 0
[80] pry(main)> Distribution::Uniform.new(3,4).cumulative_function(3.5)
=> 0.5
[81] pry(main)> Distribution::Uniform.new(3,4).cumulative_function(5)
=> 1

Probability density function

Given an interval at initialize time, calculate the density for the specified value that belongs to the interval. If the value is outside the given internal, it returns zero.

[63] pry(main)> uniform_dist = Distribution::Uniform.new(3,6)
=> #<Statistics::Distribution::Uniform:0x007fdfcbe161c8 @left=3.0, @right=6.0>
[64] pry(main)> uniform_dist.density_function(4) # interval: [3, 6]
=> 0.3333333333333333
[65] pry(main)> uniform_dist.density_function(7) # interval: [3, 6]
=> 0

Mean

It returns the expected mean value for the uniform distribution.

[66] pry(main)> uniform_dist.mean
=> 4.5

Variance

It returns the expected variance value for the uniform distribution.

[67] pry(main)> uniform_dist.variance
=> 0.75