Logistic Map and cobweb diagrams

In summary, the discussion focused on investigating the stability of a fixed point in a logistic map by plotting the function g(x) and the straight line y=x. The goal was to determine if the system evolves to a stable solution and if so, what value of x it converges to. To do this, an initial value of x was chosen and a vector of values was calculated using the logistic map equation. The project is due on Friday and it was suggested to refer to the chapter on Deterministic Chaos in the book "Chaos" by Peitigen for more information.
  • #1
S.Parker
4
0
Hi all. I am new here and I am having difficulty figuring out what exactly is required of me in this question. If someone could be so kind as to explain. For this part of the project we will consider the evolution of a discrete dynamical system given by a logistic map.
We will consider a logistic map given by

xn+1 = 2xn(1- xn) (1)

on the interval x 2 [0; 1]. A fixed point of this equation is obtained when xn+1 = xn, i.e. when

x = 2x(1 - x):

If we let

g(x) = 2x(1 - x)

then a fixed point is obtained when

x = g(x):

In our case, we can solve for this analytically, but we will investigate how a numerical solution will converge on
the solution. What we want to know is
Does the system evolve to a stable solution? i.e. is the fixed point stable?
If so, what value of x does the system evolve to?
To see how this works, essentially we will find the intersection of the straight line y = x with the function
g(x). Start by plotting y = x and g(x) on the same se of axes. Now let us start with an initial value of x and
see how the system evolves from there. Choose a suitable value of N for the number of iterations. Choose
2
x0 = 0:01, and then calculate each new value of xn from this starting value, using (1). Do this by creating a vector
x = [x0; x1; x2; : : : xN]. Plot a graph of x vs step number n. This will show you how x evolves with each new

Homework Equations

The Attempt at a Solution


To be honest, I have not tried it yet, as I am not sure of what to do exactly. I know this part is required, but I really do need the help (project due this Friday)
 
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  • #2
S.Parker said:
I am not sure of what to do exactly. I know this part is required, but I really do need the help (project due this Friday)

I believe the best approach is for you to find "Chaos" by Peitigen and go directly to the chapter on Deterministic Chaos. Never heard it called cob webs but you'll see what they're doing with the logistic map which I guess looks like webs.
 

1. What is a Logistic Map?

The logistic map is a mathematical model that is used to describe the population growth of a species. It takes into account factors such as carrying capacity and competition for resources to predict how a population will change over time.

2. How is a Logistic Map used in ecology?

In ecology, the Logistic Map is used to study population dynamics and to understand how a species' population will change over time. It can help predict if a population will grow, decline, or reach a stable equilibrium.

3. What is a cobweb diagram?

A cobweb diagram is a visual representation of the logistic map. It shows the trajectory of a population over time, starting from an initial population size and following the logistic equation. It is called a "cobweb" diagram because the lines resemble a spider's web.

4. How is a cobweb diagram used in studying population dynamics?

Cobweb diagrams are useful in studying population dynamics because they provide a visual representation of how a population will change over time. By plotting the population size on the x-axis and time on the y-axis, it is easy to see if a population will reach a stable equilibrium or undergo fluctuations.

5. Are there any limitations to using the Logistic Map and cobweb diagrams in ecology?

While the Logistic Map and cobweb diagrams are useful tools in studying population dynamics, they are based on simplified assumptions and may not accurately reflect the complexities of real-life ecosystems. Additionally, they do not take into account external factors such as environmental changes and human impacts, which can greatly affect population dynamics.

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