index must be a positive integer or logical.

clear all;
close all;
clc;
% solving the logistic growth model
% applying the forward Euler method
% definition of the right hand side
% using handles for a function 
f=@(x) b*x*(100-x);
% defining the initial condition
k=0.45;
y=10;
n=50;
tmin=0;
tmax=25;
h=(tmax-tmin)/n;
t=[tmin zeros(0,n)];
y=[y zeros(0,n)];
for i=1:n  
    t(i+1)=t(i)+h;
    y(i+1)=y(i)+h(y(i),k) 
end
% visualization of results
T = table(t,y)
plot(t,y,'o')
[p,~,mu] = polyfit(T.t, T.y, 5);
finter = polyval(p,t,[],mu);
hold on
plot(t,finter)
hold off

I keep running this code and receiving

Attempted to access h(10,0.45); index must be a positive integer or logical.

Answer 1

[Star Strider]

‘I keep running this code and receiving "Attempted to access h(10,0.45); index must be a positive integer or logical."’

The second index, 0.45 is not an integer.

[Sam Menendez]

even with number 1 it then says its out of bounds

[Walter Roberson]

It would be out of bounds if that dimension were empty.

[Walter Roberson]

Your h is (tmax-tmin)/h which is a scalar . Why are you trying to index a scalar?

Answer 2

[Chad Greene]

In the loop you try to evaluate

y(i+1)=y(i)+h(y(i),k)

but k equals 0.45, so that's the problem. Calling

h(10,0.45)

does not work because it's trying to access the 10th row of h and the 0.45th column of h.