Plot Population growth function with different values of b using for loop

I need to plot population growth model with different values of b

where b>d

and b=d

using for loops. Both results should be visible on the same graph with different colors.

Here is my function and intial value, but I am not getting how to get the plot .

H=@(t,N)[b*N-d*N];

[T,Y]=ode45(H,[0:1:time],[N0]);

Intitial value

b= 0.1 0.001

d=0.001

N0=400

I need two line for each b on the same plot.

Answer 1

[Torsten]

f = @(t,b,d,N0) N0*exp((b-d)*t);
t = 0:0.1:10;
N0 = 400;
b = [0.1 0.001].';
d = 0.001;
plot(t,f(t,b,d,N0))
grid on

[Saira]

As per requirement, I have to use forloop and ODE function. and T should be from 0 to 400. Sorry forget to mention

[Torsten]

b = [0.1 0.001];
d = 0.001;
N0 = 400;
time = 400;
hold on
for i = 1:numel(b)
    H=@(t,N)[b(i)*N-d*N];
    [T,Y] = ode45(H,[0:1:time],[N0]);
    plot(T,Y)
end
hold off
grid on

[Saira]

Thanks, I was getting the same results.

But when I try an individual plots by putting b=.01, and b=.001. I get the results as attached. and you can see the plots dimentions are totally different. They should be same, either by putting in the seperate function or function inside a loop.

[Saira]

Why you are too getting totally different plots for the same function and same inputs?

[Torsten]

Show us the two codes for which you mean you get different results for the same input.

Include them as text here, not as a PNG file.

[Saira]

function[T,Y]=model_growth(par,time)

b=par(1);

d=par(2);

N0=par(3);

H=@(t,N)[b*N-d*N];

[T,Y]=ode45(H,[0:1:time],[N0]);

end

Commands: when b=d

par=[0.01 0.01 400];

time=500;

[~,Y]=model_growth(par,time)

plot(T,Y)

and

par=[0.01 0.001 400];

time=500;

[~,Y]=model_growth(par,time)

plot(T,Y)

[Torsten]

I don't understand your point.

The parameters are different for the two cases - so the results are different.

[Saira]

You are right, I think that was what I was doing wrong. but

par=[0.01 0.01 400];

time=500;

[T,Y]=model_growth(par,time)

plot(T,Y)

This gives a straight line at 400 point when I use it in indivdual function, but at 0 when in a loop. Can you elaborate, what is going on here.

[Torsten]

Maybe 400 looks like 0 in the loop plot because the second plot gives such large results for N.

Look at the plot from my code above. The red line looks like 0 because the blue line gets up to about 7e19, but is 400.

[Saira]

Thank you so much.

I have just started coding so don't know these subtle changes.