Re: Strange Manipulate+ContourPlot behavior

*To*: mathgroup at smc.vnet.net*Subject*: [mg82172] Re: Strange Manipulate+ContourPlot behavior*From*: Yaroslav Bulatov <yaroslavvb at gmail.com>*Date*: Sat, 13 Oct 2007 04:05:49 -0400 (EDT)*References*: <fei3de$qn1$1@smc.vnet.net><200710110416.AAA21323@smc.vnet.net>

I suspect the discrepancy between "Manipulate[ContourPlot[e" and "Manipulate[ContourPlot[Evaluate[e" has to do with automatic simplification rules. The expression being plotted evaluates to 1, 0, 1/2 or Indeterminate depending on the order in which replacement rules are applied. e = (b (a - a p + b p))/(2 a b + (a - b)^2 p); rules = {a -> 0, b -> 0, p -> 0}; Fold[ReplaceAll[#1, #2] &, e, #] & /@ Permutations[rules] Is it possible to disable automatic simplification rules to prevent expressions like a / (2 a) simplifying to 1/2? On Oct 12, 12:11 am, Syd Geraghty <sydgerag... at mac.com> wrote: > Not so weird... > > In[]:= a = 0; b = 0; p = 0; (b (a - a p + b p))/(-2 a b (-1 + p) + > a^2 p + b^2 p) > > Out[]:= Indeterminate > > Syd > > Syd Geraghty B.Sc., M.Sc. > sydgerag... at mac.com > San Jose, CA > > On Oct 10, 2007, at 9:16 PM, Will Robertson wrote: > > > On Oct 10, 5:44 pm, Yaroslav Bulatov <yarosla... at gmail.com> wrote: > >> Manipulate[ > >> ContourPlot[( > >> b (a - a p + b p))/(-2 a b (-1 + p) + a^2 p + b^2 p), {a, 0, 1}, > >> {b, > >> 0, 1}], {p, 0, 1}] > > > That is weird. Sticking in an Evaluate[] around the expression fixes > > the problem -- until the slider is first moved. I guess I'd just > > recommend avoiding p = 0 ... :) > > > Will

**References**:**Re: Strange Manipulate+ContourPlot behavior***From:*Will Robertson <wspr81@gmail.com>