lib/distribution/t/ruby.rb in distribution-0.4.0 vs lib/distribution/t/ruby.rb in distribution-0.5.0

@@ -12,19 +12,24 @@
       end
       
       # t-distribution ([1])
       # (-\infty, x]
       def p_t(df, t)
+        if df.to_i!=df
+          raise "Can't calculate not integer df"
+        end
+        df=df.to_i
         c2 = df.to_f / (df + t * t);
         s = Math.sqrt(1.0 - c2)
         s = -s if t < 0.0
         p = 0.0;
         i = df % 2 + 2
         while i <= df
           p += s
           s *= (i - 1) * c2 / i
           i += 2
         end
+        
         if df.is_a? Float or df & 1 != 0
           0.5+(p*Math.sqrt(c2)+Math.atan(t/Math.sqrt(df))) / Math::PI
         else
           (1.0 + p) / 2.0
         end
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