2 views (last 30 days)

Array indices must be positive integers or logical values.

Error in Drift (line 12)

X(h) = X(0) + mu*h + sigma*Z;

for the following code...

T = 10;

N = 100;

h = T/N;

mu = 0.1;

sigma = 0.2;

X = zeros(1,N+1);

for k = 1:100

for i = 1:N+1

Z = normrnd(0,h);

X(h) = X(0) + mu*h + sigma*Z;

end

plot(Time,X);

hold on

end

John D'Errico
on 27 Sep 2019

MATLAB has an index origin of 1, not 0. So X(0) will fail, and give you exactly that error. (Matt pointed that out.)

But also

T = 10;

N = 100;

h = T/N;

...

X = zeros(1,N+1);

X(h) = X(0) + mu*h + sigma*Z;

What is h? h=10/100 = 0.1.

X is a vector. Can you index a vector at the 0.1 location? Where is that? Sort of between location 0 (which does not even exist in MATLAB anyway) and memory location 1?

Sorry. Start with the getting started tutorials. You need to learn how MATLAB does indexing.

Sign in to comment.

Sign in to answer this question.

Opportunities for recent engineering grads.

Apply Today
## 1 Comment

## Direct link to this comment

https://au.mathworks.com/matlabcentral/answers/482491-why-do-i-keep-getting-the-error-message-array-indices-must-be-positive-integers-or-logical-values#comment_750619

⋮## Direct link to this comment

https://au.mathworks.com/matlabcentral/answers/482491-why-do-i-keep-getting-the-error-message-array-indices-must-be-positive-integers-or-logical-values#comment_750619

Sign in to comment.