## Trouble with difference equation

### Debanita Das (view profile)

on 22 May 2019
Latest activity Commented on by Debanita Das

on 22 May 2019

### Raj (view profile)

clc; close all; clear all;
b=0.9; d=0.25;
nn=200;
t=[0:0.1:100];
for a=0:0.01:11
for n=1:nn
x(1)=0.4;
y(1)=2.9;
x(n+1)=x(n)+(d*((a*x(n))*(1-x(n))-((b*x(n)*y(n))/(x(n)+y(n)))));
y(n+1)=y(n)+(d*(((b*x(n)*y(n))/(x(n)+y(n)))-y(n)));
stem(y,x)
end
end
i have been trying to run this code in order to plot difference equation curves but this code isn't yielding any output. Can anyone suggest any other codes or point out my mistake?

on 22 May 2019
Edited by Raj

### Raj (view profile)

on 22 May 2019

1) For which value of 'a' are you trying to plot the stem graph? If for all the values from a=0:0.01:11 then shift the plot outside first for loop like this:
for a=0:0.01:11
for n=1:nn
x(1)=0.4;
y(1)=2.9;
x(n+1)=x(n)+(d*((a*x(n))*(1-x(n))-((b*x(n)*y(n))/(x(n)+y(n)))));
y(n+1)=y(n)+(d*(((b*x(n)*y(n))/(x(n)+y(n)))-y(n)));
end
stem(y,x)
hold on
end
If you want to plot for a particular value of 'a' then the first for loop makes no sense.
2) what is the use of 't'?
3) Use of close all, clear all etc are not recommended. See here.

Debanita Das

### Debanita Das (view profile)

on 22 May 2019
Thank you so much for rectifying my mistake.