Compare vector to two other vectors

2 次查看（过去 30 天）
DucciVinci
DucciVinci 2023-3-9
回答： DucciVinci 2023-3-9
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 个评论
Dyuman Joshi
Dyuman Joshi 2023-3-9
"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.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

DucciVinci
DucciVinci 2023-3-9
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.

更多回答（2 个）

David Hill
David Hill 2023-3-9
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 2023-3-9
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.

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by