Array indices must be positive integers or logical values
2 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
I have this MatLab code where I want to run a metropolis algorithm.
In my s rho is a matrix 12x12 and L is a matrix 12x12. m0 is a vector 1x12.
When I run my code I got the error 'Array indices must be positive integers or logical values' in hfuncval(1) where I want to compute s in the starting point.
How can come throught that?
Thank
s = -0.5.*(rho + L);
% (4) Metropolis algorithm
K = 10000; %Number of samples
pts = zeros(length(m0),K); %Array with sample output points
hfuncval = zeros(K); %Array with function value outputs
pts(:,1) = m0; %Set starting points
hfuncval(1) = s(pts(:,1)); %Compute function in starting point
step = 0.5; %Set step length
%Start sampling
for k = 1:K
[ptpert] = pts(:,k-1) + (2*rand(2,1)).*step; % propose perturbed point
hfuncpert = hfunc(ptpert); % Compute function in perturbed point
u = rand; % Generate random number in [0,1]
if u < hfuncpert/hfuncval(k-1) % accepting new points
% if u < exp(log(hfuncpert)-log(hfuncval(k-1)))
pts(:,k) = ptpert;
hfuncval(k) = hfuncpert;
else % Rejecting new points
pts(:,k) = pts(:,k-1);
hfuncval(k) = hfuncval(k-1);
end
end
The theory of the algorithm is:
![a.png](https://www.mathworks.com/matlabcentral/answers/uploaded_files/260694/a.png)
6 commentaires
Rik
le 9 Jan 2020
Look at the values of ptpert at that point. Use the debugging tools to step through your code line by line.
Réponses (1)
the cyclist
le 8 Jan 2020
In this line:
hfuncval(k) = hfuncval(k-1);
in the first iteration of the for loop, k == 1, so you are attempting to access the "zeroth" element of the array hfuncval, which does not exist.
9 commentaires
the cyclist
le 9 Jan 2020
I have to admit I have not reviewed your code closely.
But the error makes it pretty clear, right? ptpert is not a positive integer, so it cannot be used as an index into a vector. For example, if ptpert is 1.5, what does sigma(1.5) represent?
It looks like the line
ptpert = pts(:,k-1) + (2*rand(12,1)-1)*step;
is where you go wrong. That doesn't look like it is going to be an integer.
Voir également
Catégories
En savoir plus sur Quantum Mechanics dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!