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Re: Manipulate a complex expression
*To*: mathgroup at smc.vnet.net
*Subject*: [mg77886] Re: Manipulate a complex expression
*From*: dh <dh at metrohm.ch>
*Date*: Tue, 19 Jun 2007 06:35:06 -0400 (EDT)
*References*: <f505ip$qug$1@smc.vnet.net> <f5332a$3lb$1@smc.vnet.net>
Hi Daniele,
if you redefine epsilonCyt to:
epsilonCyt:=(Print[{conductivityCyt}];complexEps[permittivityCyt,conductivityCyt,omega]);
you will see that conductivityCyt is never replaced by a numerical
value. Therefore, we must conclude that Manipulate localizes
conductivityCyt before the Evaluate is done. To prevent this, you must
give conductivityCyt as an argument:
epsilonCyt[conductivityCyt_] := Im[complexEps[permittivityCyt,
conductivityCyt, omega]];
the the following will work:
Manipulate[Plot[epsilonCyt[conductivityCyt],{f,1 10^5,1
10^10}],{conductivityCyt,0.1,0.5}]
hope this helps, Daniel
Daniele wrote:
> Hello,
> as a follow up to my previous post, I think I can clarify my question
> with a simpler example.
>
> Once I define the following:
>
> complexEps[permittivity_, conductivity_, omega_] := permittivity - (I
> conductivity/omega);
> epsilonCyt := complexEps[permittivityCyt, conductivityCyt, omega];
> omega := 2 Pi f
> permittivityCyt := 50;
>
> Why does this work:
>
> Manipulate[Plot[Im[Evaluate[complexEps[permittivityCyt,
> conductivityCyt, omega]]], {f, 1 10^5,1 10^10}], {conductivityCyt,
> 0.1, 0.5}]
>
> While this doesn't:
>
> Manipulate[Plot[Im[Evaluate[epsilonCyt]], {f, 1 10^5, 1 10^10}],
> {conductivityCyt, 0.1, 0.5}]
>
> I would think that the two 'Manipulate' expressions would be
> equivalent, but obviously I'd be wrong....
>
> thanks.
>
> On 16 Jun, 09:04, Daniele <d.mal... at gmail.com> wrote:
>> Hello,
>> I'm trying to use the new Manipulate function to evaluate a complex
>> expression. I'm getting a headache, as I'm not familiar with the
>> Mathematica notation (I do most of my work, numerically, with another system).
>> Maybe somebody here can help debug these few lines?
>>
>> The expression I want to 'manipulate' is the following:
>>
>> MeasuredCMF := VolumeFraction ( EpsilonCell - EpsilonMedium)/
>> ( EpsilonCell + 2 EpsilonMedium)
>>
>> Where VolumeFraction is a parameter, and the other variables are
>> complex and a function of 'f'.
>> They are defined below.
>>
>> omega := 2 Pi f
>> EpsilonCyt := PermittivityCyt - ( ConductivityCyt/omega) I
>> EpsilonMembrane := PermittivityMembrane - (ConductivityMembrane/omega)
>> I
>> EpsilonMedium := PermittivityMedium - (ConductivityMedium/omega) I
>>
>> CMFCell := ( EpsilonCyt - EpsilonMembrane)/( EpsilonCyt + 2
>> EpsilonMembrane)
>> v := CellRadius/(CellRadius - MembraneThickness)
>> EpsilonCell := EpsilonMembrane *(v^3 + 2 CMFCell)/(v^3 - CMFCell)
>>
>> Epsilon0 = 8.85 10^-12;
>> PermittivityCyt = 120 Epsilon0;
>> PermittivityMembrane = 6 Epsilon0;
>> PermittivityMedium = 80 Epsilon0;
>> ConductivityCyt = 0.15;
>> ConductivityMedium = 0.15;
>> ConductivityMembrane = 1 10^-9;
>> CellRadius = 10 10^-6;
>> MembraneThickness = 9 10^-9;
>>
>> if I define VolumeFraction (eg. VolumeFraction=0.1) and plot
>> Re[MeasuredCMF] vs. f, I have no problem.
>> But I am unable to successfully do the following (I get a blank plot)
>>
>> Manipulate[
>> LogLinearPlot[
>> Evaluate[Re[MeasuredCMF]], {f, 1 10^5, 1 10^9}], {{VolumeFraction,
>> 0.2}, 0.1, 0.5}]
>>
>> Can somebody help? I suspect I'm not using the assignment syntax
>> correctly.
>> Thanks
>>
>> Daniele Malleo
>
>
>
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