lib/distribution/t/ruby.rb in distribution-0.5.0 vs lib/distribution/t/ruby.rb in distribution-0.6.0

@@ -13,10 +13,11 @@
       
       # t-distribution ([1])
       # (-\infty, x]
       def p_t(df, t)
         if df.to_i!=df
-          raise "Can't calculate not integer df"
+          x=(t+Math.sqrt(t**2+df)) / (2*Math.sqrt(t**2+df))
+          return Math.regularized_beta(x,df/2.0,df/2.0)
         end
         df=df.to_i
         c2 = df.to_f / (df + t * t);
         s = Math.sqrt(1.0 - c2)
         s = -s if t < 0.0
\ No newline at end of file