how to find out how many times a number apears in a 2D matrix ? which function to use?

4 次查看（过去 30 天）
aya qassim
aya qassim 2019-1-5
编辑： madhan ravi 2019-1-7
Hey,
how can I find how many time a numbers appears in an 2D matrix for example:
If I have a matrix
x=[1,3,4;2,2,1;2,2,1]
number 2 appears 4 times
numger 1 appears 2 times
number 3 appears 1 time
Desired output:
22 1 3
22 1
  1 个评论
Image Analyst
Image Analyst 2019-1-7
编辑：Image Analyst 2019-1-7
You can't have an array with ragged right edge. Arrays must be rectangular. What do you want in the space below the 3? Or else you could have a 1-by-3 cell array, ca where
ca{1} = [2, 2; 2, 2];
ca{2} = [1;1];
ca{3} = 3;
Is that what you want?
Anyway, 1 appears 3 times, not 2 times, and what about 4? Why is 4 not in your desired output?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

madhan ravi
madhan ravi 2019-1-5
n=2; % number to be tested
nnz(ismember(x,n))
  2 个评论
aya qassim
aya qassim 2019-1-6
编辑：madhan ravi 2019-1-7
thank you,
But if I only have the matrix as an input (I don't have an input fot the number ) , how can I find out how many time a number apprears?
madhan ravi
madhan ravi 2019-1-7
编辑：madhan ravi 2019-1-7
Try the below , a in result represent unique numbers and the corresponding histc() shows how many times they occur in the matrix:
a = unique(x);
result = [a histc(x(:),a)]

请先登录，再进行评论。

更多回答（1 个）

Walter Roberson
Walter Roberson 2019-1-6
[ux, ia, ic] = unique(x);
output = [ux, accumarray(ic, 1)]

类别

在 Help Center 和 File Exchange 中查找有关 Resizing and Reshaping Matrices 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