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Malthusian Equation Help

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Join Date: Oct 2004

Posts: 6

Reputation: Eclipse is an unknown quantity at this point

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Eclipse

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Newbie Poster

Malthusian Equation Help

Nov 17th, 2004

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P = R*P*(1-P)

Input: R (growth rate parameter) Double values between 0 and 10.

Input: P (population) Double values between 0 and 1.

Output: P (New population) on the console in rows of five numbers

the exit conditions are the population becomes extinct or stable.

Extinction occurs when the new value of P is zero.

Stability occurs when the new value of P is the same as the previous value of P.

Hey...okay, I really don't need much coding help for this, but I need some JAVA logic help. Once I understand the logic, I think I'll be able to get it. So basically, I need to create two methods I suppose, but I don't get the basis of this equation at all!!! This seems more like a math problem than a programming problem.

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Join Date: Nov 2004

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jwenting

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duckman

Re: Malthusian Equation Help

Nov 17th, 2004

It is.
But you didn't even tell what the problem is.
Do you want to determine values of R for which a given P will yield a stable population?
Or maybe values of P for which a given R will yield a stable population?
Or what exactly do you want?

Once you know that you can start designing your code around that knowledge.

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Join Date: Jul 2004

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nanosani

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Re: Malthusian Equation Help

Nov 17th, 2004

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
 
Method( double R, double P){
 
   P = R*P*(1-P);
 
   return P;
}
Method( double R, double P){

   P = R*P*(1-P);

   return P;
}

Is this what you want to do ??

http://www.technize.com

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Join Date: Sep 2004

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jerbo

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Junior Poster in Training

Re: Malthusian Equation Help

Nov 17th, 2004

You want to set up a loop. Save your initial 'P' value, then feed it back into the equation. Then check the result and determine if it is stable or Extinct.

You can put the below in it's own method called 'Malthusian':

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public int Malthusian {
   double saveP;
   double newP;
   boolean bflag = true;
   int returnVal = 0; // Initial value
 
   // Assuming nano's method above returns a double: 
   saveP = Method(5,1);
   while(bflag) {
      newP = Method(5,saveP);
      if (newP == saveP) {
         // Stable (do what you need to return this.)
         returnVal = 1;  // Arbitrary value to denote Stable
         bflag = false;
      }
      if (P == 0) {
         // Extinct (do what you need to return this.)
         returnVal = 2;  // Arbitrary value to denote Extinct
         bflag = false;
      }
      return returnVal;  // Return the value
   }
}
public int Malthusian {
   double saveP;
   double newP;
   boolean bflag = true;
   int returnVal = 0; // Initial value

   // Assuming nano's method above returns a double: 
   saveP = Method(5,1);
   while(bflag) {
      newP = Method(5,saveP);
      if (newP == saveP) {
         // Stable (do what you need to return this.)
         returnVal = 1;  // Arbitrary value to denote Stable
         bflag = false;
      }
      if (P == 0) {
         // Extinct (do what you need to return this.)
         returnVal = 2;  // Arbitrary value to denote Extinct
         bflag = false;
      }
      return returnVal;  // Return the value
   }
}