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

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Jose 2014-8-19

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编辑： Matt J 2014-8-19

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

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Answer 1

Matt J 2014-8-19

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https://ww2.mathworks.cn/matlabcentral/answers/151472-attempted-to-access-t-2-index-out-of-bounds-because-numel-t-1#answer_149075

在 MATLAB Online 中打开

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.

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Answer 2

Jose 2014-8-19

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https://ww2.mathworks.cn/matlabcentral/answers/151472-attempted-to-access-t-2-index-out-of-bounds-because-numel-t-1#answer_149079

I still cant figure it out :(

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Jose 2014-8-19

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

Matt J 2014-8-19

编辑：Matt J 2014-8-19

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.

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Answer 3

Guillaume 2014-8-19

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https://ww2.mathworks.cn/matlabcentral/answers/151472-attempted-to-access-t-2-index-out-of-bounds-because-numel-t-1#answer_149081

编辑：Guillaume 2014-8-19

在 MATLAB Online 中打开

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.

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Jose 2014-8-19

编辑：Jose 2014-8-19

在 MATLAB Online 中打开

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