Compare vector to two other vectors

2 visualizzazioni (ultimi 30 giorni)
DucciVinci
DucciVinci il 9 Mar 2023
Risposto: DucciVinci il 9 Mar 2023
I'm struggling with the following binning task:
I have three vectors of different sizes k, m and n. My goal is to get an -matrix in which the -th entry simply counts how many elements from the k-vector are simultaneously smaller than both and .
So basically I want to do something like but with one of the inputs as a matrix rather than a vector.
Is there an efficient way to do this?
Of course I can and have also done it with a loop, but that seems terribly inefficient especially since the k from my simplified example is actually really large. Trying to write everything in -Matrices results in too large arrays unfortunately.
Thanks in advance!
  1 Commento
Dyuman Joshi
Dyuman Joshi il 9 Mar 2023
"Of course I can and have also done it with a loop..."
Can you show what have you tried?
Also, please attach your data using the paperclip button. It will be helpful in providing an answer to your problem.

Accedi per commentare.

Risposta accettata

DucciVinci
DucciVinci il 9 Mar 2023
Ah I'm sorry, I completely forgot about matrix multiplication.
Solution actually is pretty simple:
Transpose the k-vector and compare with both other vectors using implicit Cartesian expansions, giving logical arrays of sizes and .
Now just transpose the -matrix and multiply, killing the k-dimension.
Not quite used to matrix multiplication with logical arrays, but it makes a lot of sense here.
Sorry to have bothered you.

Più risposte (2)

David Hill
David Hill il 9 Mar 2023
m=randi(100,1,20);
n=randi(100,1,30);
k=randi(100,1,10000);
[M,N]=meshgrid(m,n);
x=min(M,N);
z=zeros(size(x));
u=unique(x);
y=sum(k<u,2);
for j=1:length(u)
z(x==u(j))=y(j);
end

Steven Lord
Steven Lord il 9 Mar 2023
I think what you want is to use histcounts2 to calculate how many numbers fall into each bin between m(k) and m(k+1) [and between n(k) and n(k+1)] then call cumsum twice, once to sum across the rows and once to sum the matrix from the previous call down the columns.

Prodotti

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by