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require File.expand_path(File.dirname(__FILE__)+"/spec_helper.rb")
include ExampleWithGSL
describe Distribution::Binomial do
shared_examples_for "binomial engine" do
it "should return correct pdf" do
if @engine.respond_to? :pdf
[10,100,1000].each do |n|
[1.quo(4),1.quo(2),3.quo(4)].each do |pr|
[0, 1,n/2,n-1].each do |x|
exp=Math.binomial_coefficient(n,x)*pr**x*(1-pr)**(n-x)
obs=@engine.pdf(x,n,pr)
obs.should be_within(1e-5).of(exp), "For pdf(#{x},#{n},#{pr}) expected #{exp}, obtained #{obs}"
end
end
end
else
pending("No #{@engine}.pdf")
end
end
it_only_with_gsl "should return correct cdf for n<=100" do
if @engine.respond_to? :pdf
[10,100].each do |n|
[0.25,0.5,0.75].each do |pr|
[1,n/2,n-1].each do |x|
exp=GSL::Cdf.binomial_P(x,pr,n)
obs=@engine.cdf(x,n,pr)
exp.should be_within(1e-5).of(obs), "For cdf(#{x},#{n},#{pr}) expected #{exp}, obtained #{obs}"
end
end
end
else
pending("No #{@engine}.cdf")
end
end
end
describe "singleton" do
before do
@engine=Distribution::Binomial
end
it_should_behave_like "binomial engine"
it {@engine.should respond_to(:exact_pdf) }
it {
pending("No exact_p_value")
@engine.should respond_to(:exact_p_value)
}
it "exact_cdf should return same values as cdf for n=50" do
pr=rand()*0.8+0.1
n=rand(10)+10
[1,(n/2).to_i,n-1].each do |k|
@engine.exact_cdf(k,n,pr).should be_within(1e-10).of(@engine.cdf(k,n,pr))
end
end
it "exact_pdf should not return a Float if not float is used as parameter" do
@engine.exact_pdf(1,1,1).should_not be_a(Float)
@engine.exact_pdf(16, 80, 1.quo(2)).should_not be_a(Float)
end
end
describe Distribution::Binomial::Ruby_ do
before do
@engine=Distribution::Binomial::Ruby_
end
it_should_behave_like "binomial engine"
it "should return correct cdf for n>100" do
pending("incomplete beta function is slow. Should be replaced for a faster one")
end
it "should return correct p_value for n<=100" do
pending("Can't calculate with precision x using p")
[10,100].each do |n|
[0.25,0.5,0.75].each do |pr|
[n/2].each do |x|
cdf=@engine.cdf(x,n,pr)
p_value=@engine.p_value(cdf,n,pr)
p_value.should eq(x), "For p_value(#{cdf},#{n},#{pr}) expected #{x}, obtained #{p_value}"
end
end
end
end
end
if Distribution.has_gsl?
describe Distribution::Binomial::GSL_ do
before do
@engine=Distribution::Binomial::GSL_
end
it_should_behave_like "binomial engine"
end
end
#if Distribution.has_statistics2?
# describe Distribution::Binomial::Statistics2_ do
#
# before do
# @engine=Distribution::Binomial::Statistics2_
# end
#it_should_behave_like "binomial engine"
# end
#end
if Distribution.has_java?
describe Distribution::Binomial::Java_ do
before do
@engine=Distribution::Binomial::Java_
end
it_should_behave_like "binomial engine"
end
end
end
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