spec/math_extension_spec.rb in distribution-0.3.0 vs spec/math_extension_spec.rb in distribution-0.4.0

@@ -6,27 +6,32 @@
     n.times do |k|
       Math.binomial_coefficient(n,k).should eq(Math.factorial(n).quo(Math.factorial(k)*Math.factorial(n-k)))
     end
   end
   
-  it "binomial coefficient(gamma) with n<=48 should be correct " do
-    
-    [1,5,10,25,48].each {|n|
-      k=(n/2).to_i
-      Math.binomial_coefficient_gamma(n,k).round.should eq(Math.binomial_coefficient(n,k))
-    }
-  end
+  
   it "rising_factorial should return correct values" do
     
     x=rand(10)+1
     Math.rising_factorial(x,0).should eq 1
     Math.rising_factorial(x,1).should eq x
     Math.rising_factorial(x,2).should eq x**2+x
     Math.rising_factorial(x,3).should eq x**3+3*x**2+2*x
     Math.rising_factorial(x,4).should eq x**4+6*x**3+11*x**2+6*x
 
   end
+  
+  it "permutations should return correct values" do
+    n=rand(50)+50
+    10.times { |k|
+      Math.permutations(n,k).should eq(Math.factorial(n) / Math.factorial(n-k))
+    }
+    
+    
+    Math.permutations(n,n).should eq(Math.factorial(n) / Math.factorial(n-n))
+  end
+  
   it "incomplete beta function should return similar results to R" do
     pending("Not working yet")
     Math.incomplete_beta(0.5,5,6).should be_within(1e-6).of(Math.beta(5,6)*0.6230469)
     Math.incomplete_beta(0.6,5,6).should be_within(1e-6).of(Math.beta(5,6)*0.0006617154)
   end
@@ -44,15 +49,25 @@
     
     Math.regularized_beta_function(x,a,b).should be_within(1e-6). of(1-Math.regularized_beta_function(1-x,b,a))
     
     
   end
-  it "binomial coefficient(gamma) with 48<n<1000 should have 12 correct digits" do 
+  
+  it "binomial coefficient(gamma) with n<=48 should be correct " do
     
-    [50,100,1000].each {|n|
-      k=n/2.to_i
-      obs=Math.binomial_coefficient_gamma(n,k).to_i.to_s[0,12]
-      exp=Math.binomial_coefficient(n,k).to_i.to_s[0,12]
+    [1,5,10,25,48].each {|n|
+      k=(n/2).to_i
+      Math.binomial_coefficient_gamma(n,k).round.should eq(Math.binomial_coefficient(n,k))
+    }
+  end
+  
+  it "binomial coefficient(gamma) with 48<n<1000 should have 11 correct digits" do 
+    
+    [50,100,200,1000].each {|n|
+      k=(n/2).to_i
+      obs=Math.binomial_coefficient_gamma(n, k).to_i.to_s[0,11]
+      exp=Math.binomial_coefficient(n, k).to_i.to_s[0,11]
+      
       obs.should eq(exp)
     }
   end
   
   describe Distribution::MathExtension::SwingFactorial do