Counting frequency of occurrence in matrix

84 次查看（过去 30 天）
Guan Zhao
Guan Zhao 2012-10-23
评论： Brian Derstine 2021-8-31
Good day,
I am attempting to count the number of times each number in a matrix occurred in the matrix.
For example, suppose I have a matrix;
x =
22 23 24 23
24 23 24 22
22 23 23 23
I want an output which will tell me 22 occurred 3 times, 23 occurred 6 times, and 24 occurred 2 times. The actual matrix is larger in size.
Is there a specific function which returns such values or are there any other ways I can resolve this challenge?
  3 个评论
显示 1更早的评论
Jerry Olup
Jerry Olup 2017-6-20
Let x be your vector. Something like this can save you an unnecessary toolbox:
xx = unique(x); % temp vector of vals
x = sort(x); % sorted input aligns with temp (lowest to highest)
t = zeros(size(xx)); % vector for freqs
% frequency for each value
for i = 1:length(xx)
t(i) = sum(x == xx(i));
end
Then the t vector shows freqs of the sorted, unique vector x.
m_vdv
m_vdv 2018-5-10
Hi, is it also possible to do this without using 'unique' and 'sort'? For example with only using a for loop and/or if loop? Thanks in advance.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Andrei Bobrov
Andrei Bobrov 2012-10-23
x =[
22 23 24 23
24 23 24 22
22 23 23 23];
a = unique(x);
out = [a,histc(x(:),a)];
  8 个评论
显示 6更早的评论
Brian Derstine
Brian Derstine 2021-8-31
would be nice if you could just do tabulate(x)

请先登录，再进行评论。

更多回答（3 个）

Aurelien Queffurust
Aurelien Queffurust 2012-10-23
Using nnz for example:
nnz(x==22)
will return 3
  1 个评论
Guan Zhao
Guan Zhao 2012-10-23
Hi,
My actual matrix will have at least 256 elements. I will have to consider zero elements too.
Regards
Guan Zhao

请先登录，再进行评论。

Thomas
Thomas 2012-10-23
x=[22 23 24 23
24 23 24 22
22 23 23 23];
[a,b]=hist(x,unique(x));
out=[b' sum((a),2)]
abdelrahim hashem
abdelrahim hashem 2017-11-15
x = [22 23 24 23; 24 23 24 22; 22 23 23 23];
un_x = unique(x);
for i = 1:length(un)
un(i), length(find(x == un_x(i)))
end

类别

在 Help Center 和 File Exchange 中查找有关 Matched Filter and Ambiguity Function 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by