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

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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
##### 1 CommentShowHide None
Stephen23 on 26 Sep 2021
MATLAB indexing starts at one, not zero.

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.

R2021a

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