How can I figure out which element in the array is repeated and how many times?

Hi every one, I have a problem with matrix.

Code:

A = {''A'', "B", ''C''; "D", "E", "F"; ''A'', "G", "H"; ''C'', "Y", "C"};

How can I figure out which element in the array is repeated and how many times?

Thanks and Best Regards,

Kiet Vo

Answer 1

[Wan Ji]

Hi, friend, using histcounts, things will be simple

A = {'A', 'B', 'C'; 'D', 'E', 'F'; 'A', 'G', 'H'; 'C', 'Y', 'C'};
A = categorical (A);
[counts, val] = histcounts(A)

Results become

counts =

     2     1     3     1     1     1     1     1     1

val =

  1×9 cell 数组

    {'A'}    {'B'}    {'C'}    {'D'}    {'E'}    {'F'}    {'G'}    {'H'}    {'Y'}

[Võ Kiet]

Very nice my friend, thanks so much for your help []~(￣▽￣)~*

[Võ Kiet]

Hi @Wan Ji,

I have another question about this topic, please help me!

If I send that matrix into another function, I want to use the number of counts of a few characters in that matrix in that function. Example: I counted two instances of the letter "A" in that function (according to the histcounts function). I'll take that number and save it in a variable that I can utilize later. But, if my input character is another character, how can my function tell?

Example:

A = {'A', 'B', 'C'; 'D', 'E', 'F'; 'A', 'G', 'H'; 'C', 'Y', 'C'};

function x = another_function(A)

A = categorical (A);

[counts, val] = histcounts(A)

m = containers.Map(val,counts)

% But in another case, I don't know which character greater than or equal to 2, so how to know which character to meet or satisfy ('C' is example because I know it greater than 2)

if m('C') > 2

x = m('C')*2;

end

end

[Wan Ji]

@Võ Kiet You can do by

function x = another_function(A)
A = categorical (A);
[counts, val] = histcounts(A);
q = counts>=2;
counts = counts(q);
val = val(q);
m = containers.Map(val,counts);
% But in another case, I don't know which character greater than or equal to 2, so how to know which character to meet or satisfy ('C' is example because I know it greater than 2)
if m('C') > 2
    x = m('C')*2;
end
end

[Võ Kiet]

Hi @Wan Ji,

Yes, your opinion is great. But in this case the key greater than 2 is A and C. If I don't know A and C, I just know there are two characters with values greater than 2, how can I tell which character has which value?

[Wan Ji]

hi, friend, just delete the last four lines of the function i last gave to you. and add a line to the end of the function as x=2*val; i think that is ok to get the result you want

[Võ Kiet]

Hi my friend @Wan Ji,

Yes, but I don't know which character it is T___T it's maybe A or C, I wanna know which character has which value...

[Wan Ji]

That's Simple to solve

function [x, characters, counts]= another_function(A)
A = categorical (A);
[counts, val] = histcounts(A);
q = counts>=2;
counts = counts(q);
characters = val(q);
x = 2*counts;
end

[Võ Kiet]

Yaaaa, I got it. Thanks so much for your support =v=