Drexel dragonThe Math ForumDonate to the Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.

Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: (amusement) surprising result from PossibleZeroQ
Replies: 0  

Advanced Search

Back to Topic List Back to Topic List  
Peter Pein

Posts: 1,147
Registered: 5/4/05
(amusement) surprising result from PossibleZeroQ
Posted: May 4, 2013 3:17 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Dear group,

playing around with distributions, I experienced one of these "that's

Take the quantile of a Pareto distribution

test = Quantile[ParetoDistribution[k, a], q];

ConditionalExpression[Piecewise[{{k/(1 - q)^a^(-1), q < 1}}, Infinity],
0 <= q <= 1]

I thought the nesting of ConditionalExpression and Piecewise could
simplify and tried every possible combination of 4 functions; to no avail:

Block[{f = {Refine, Simplify, FullSimplify, PiecewiseExpand}},
Length[funcs =
Composition @@@ Flatten[Tuples[f, #] & /@ Range[Length@f], 1]]

DeleteCases[Through[funcs[test]], test]

My expectation has been sth. like

test2 = Piecewise[{{k/(1 - q)^(1/a), 0 <= q < 1},
{Infinity, q == 1}},


FullSimplify[test2 - test] // InputForm
ConditionalExpression[0, 0 <= q <= 1]

looks good. But compare this to

PossibleZeroQ[test2 - test] // InputForm
ConditionalExpression[False, 0 <= q <= 1]

I decided to classify that as "funny" :)

MemberQ[Attributes@PossibleZeroQ, Listable]

Have fun with or without Mathematica!


Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum 1994-2015. All Rights Reserved.