first draft of Binomial.icdf issue #6612

pymc/distributions/discrete.py

@@ -173,6 +173,10 @@ def logcdf(value, n, p):
             msg="n >= 0, 0 <= p <= 1",
         )
 
+    def icdf(value, n, p):
+        cdf_vals = Binomial.logcdf(pt.arange(0, n), n, p)
+        return pt.argmax(cdf_vals > pt.log(value))
+
 
 class BetaBinomial(Discrete):
     R"""