Error Array indices must be positive integers or logical values. when doing euler's method.

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Kaitlyn Plutt
Kaitlyn Plutt on 26 Sep 2021
Answered: Shanmukha Voggu on 29 Sep 2021
I am tyring to do euler's method with the logistic function dx/dt= xr(1-x/L). Where r=0.65 and L=5.4, intial value is x(0)=6 and t (0,30), and h=0.5. This is my code as of now( I have tried a bunch of different codes giving me the same error).
h=1/2;
N=60;
x(0)=6;
r= 0.65;
L=5.4;
dx= @(x)(r*x)*(1-x/L)
for n=0:N
t(n+1)=t(n)+h;
x(n+1)=x(n)+h*dx(x(n));
end
%I also tried it with
h=1/2;
N=60;
x(0)=6;
r= 0.65;
L=5.4;
dx= @(t,x)(r*x)*(1-x/L)
for n=0:N
t(n+1)=t(n)+h;
x(n+1)=x(n)+h*dx(t(n), x(n));
end

Answers (1)

Shanmukha Voggu
Shanmukha Voggu on 29 Sep 2021
Hi Kaitlyn,
The error you are facing is due to accessing the zeroth index of the vector
t=[14 6 3] % creating a simple vector
t = 1×3
14 6 3
firstElement=t(1) % first element of the array is accessed by index "1"
firstElement = 14
t(0) %produces error because zeroth index is not available
Array indices must be positive integers or logical values.
Refer to this for more information

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