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MathGroup Archive 2007

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Re: Solving differential equations with parameters

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79835] Re: Solving differential equations with parameters
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Mon, 6 Aug 2007 03:38:09 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <f91j5e$677$1@smc.vnet.net> <f9445k$mdg$1@smc.vnet.net>

Ivan wrote:
> On Aug 4, 12:07 pm, Ivan <darkna... at gmail.com> wrote:
>> Hi, I am trying to solve the differential equations like
>>
>> y'[x]= - Sin[ p*x + y[x] ]
>>
>> where p is a parameter. Now I want to solve the equation with respect
>> to x for a range of values of p, instead for just a single p.
>> What is the best way to do it?
> 
> I now have a way to do it but there is another problem..
> 
> I use the Table command (I change the function for the sake of
> demonstration)
> 
> sol = NDSolve[{y'[x]==1/2y[x],y[0.01]==0.1}, y, {x, 0.01,1}];
> 
> g=Table[ {y[i*0.01]/.sol}, {i,100} ];
> 
> ListPlot[g];
> 
> The error message is gptn: Coordindate .. in ... is not a floating-
> point number.
> 
> The problem seems to be that y[x]/.sol generate not a "normal" number,
> instead, the number is is a brace {...}.
> 
> Can anyone help me?

Use y[x]/.sol[[1]] or y[x]/.First[sol]

Regards,
Jean-Marc


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