" Attempted to access t(2); index out of bounds because numel(t)=1."

Need your help once again :) I am getting this error which I dont know what it means. I am trying to write a code on Euler's method for my homework. " Attempted to access t(2); index out of bounds because numel(t)=1."

%%Tasks
clc, clear all
func = @(t,x) -t.*x;

t = 0; %Initial Value
x = 1; %Initial Value
h = 0.1; %Step size
N = 10;
tarrays = zeros(1,N)
xarrays = zeros(1,N)

for i = 1:N
    x(i+1) = x(i) + h.*func(t(i),x(i));
    tarrays = t(i)
    xarrays = x(i+1)
end

Answer 1

[Matt J]

It means you've done something like this,

 >> t=1:5; a=t(6)
 Attempted to access t(6); index out of bounds because numel(t)=5.

Use the dbstop command and its cousins to locate the error.

Answer 2

[Jose]

I still cant figure it out :(

[Matt J]

What happened when you used dbstop?

[Jose]

It just says "index exceeds matrix dimensions" I dont know how and where

[Matt J]

Don't you see a "K>>" prompt?

[Jose]

Error in lab6 (line 15) x(i+1) = x(i) + h.*func(t(i),x(i));

[Matt J]

It just says "index exceeds matrix dimensions" I dont know how and where

The error message tells you where the error is (line 15). It also tells you why (my Answer above).

But you clearly didn't use DBSTOP or refer to the other debugging commands I pointed you to if you haven't reached a K>> prompt.

Answer 3

[Guillaume]

There are lots of problems with your loop:

    x(i+1) = x(i) + h.*func(t(i),x(i));

is the cause of the error. You've defined t as a scalar (t=0; %Initial Value) and then access it as an array. t only has one element, therefore t(i) when i==2 is invalid.

    tarrays = t(i)

Even if t was array, t(i) would be a scalar. You would then overwrite your predefined tarrays with that scalar. Each loop tarrays would just be a scalar containing t(i). At the end tarrays would just be t(N).

    xarrays = x(i+1)

Same problem as with tarrays.

[Jose]

so I rewrote

   %%Tasks
  clc, clear all
  %func = @(t,x) -t.*x;
  func = @(t,x) sinh(x ./ (t+1));
  % func = @(t,x) (t*x.^2)*cos(x.^2);

t0 = 1; %Initial Value
x = 1; %Initial Value
h = 0.1; %Step size
N = 10;
tarrays = zeros(1,N)
xarrays = zeros(1,N)

for i = 1:N
    t = t0
    x(i+1) = x(i) + (h*func(t(i),x(i)))
    xarrays = x
    tarrays = t

end

I am not sure what to do about your first statement though.