fill matrix with all options of successive, increasing numbers 1-5

16 vues (au cours des 30 derniers jours)
Sjoukje de Lange
Sjoukje de Lange le 25 Jan 2021
I want to construct a matrix, m x n, filled with the numbers 1 till 5. The numbers have to be successive, and have to be increasing. One column of the matrix could for example look like.
A =1 1 2 2 2 2 3 4 5 5 5 5
or
A = 1 2 3 3 3 4 5 5 5 5 5 5
I want to construct a matrix with all possible options. The first column of matrix A therefore should look like this:
A(:,1) = 1 1 1 1 1 1 1 1 2 3 4 5
and the last one like this
A(:,end)= 1 2 3 4 5 5 5 5 5 5 5
In my case, the matrix will have a length of 96, instead of the above example where the length is 12. Could you help me?
  8 commentaires
Adam Danz
Adam Danz le 25 Jan 2021
Modifié(e) : Adam Danz le 25 Jan 2021
Why do you need repeated values, then?
There are 61,124,064 ways to select 5 items out of 96 and that's without repetition. With the repetitions you're looking at billions.
Addendum: the number above includes indicies that increase and decrease. If you're only interested in increading indicies, that number will be reduced.
Sjoukje de Lange
Sjoukje de Lange le 25 Jan 2021
Hmmm that might be a but extreme yeah... I need repeating values because I want to label each parameter at each kilometer with number 1-5.

Connectez-vous pour commenter.

Réponse acceptée

Bruno Luong
Bruno Luong le 25 Jan 2021
Modifié(e) : Bruno Luong le 25 Jan 2021
p = 5;
n = 12;
j = nchoosek(2:n,p-1);
m = size(j,1); % == nchoosek(n-1,p-1) == 330 and not 96
i = repmat((1:m)',1,p-1);
A = cumsum(accumarray([i(:) j(:)],1,[m n]),2)+1
  4 commentaires
Adam Danz
Adam Danz le 25 Jan 2021
Modifié(e) : Adam Danz le 25 Jan 2021
Nice one (+1)
When n==96, A has 3,183,545 rows and takes less than 3 sec using the same machine as above.
Sjoukje de Lange
Sjoukje de Lange le 26 Jan 2021
neat! Amazing!

Connectez-vous pour commenter.

Plus de réponses (0)

Catégories

En savoir plus sur Sparse Matrices 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!

Translated by