How to count number of occurences of each value in a vector and put the number beside the value as a new column?

I have vector (3079X1).

I want to count the number of occurrences of each value within the vector and put that number beside the respective value of the vector. I have tried using groupcount but it reorders the result in ascending order. I want to keep the same order as it was in the original vector.

Answer 1

[Stephen23]

>> V = randi(9,13,1)
V =
   6
   4
   4
   2
   9
   5
   1
   6
   2
   1
   6
   9
   4
>> [N,X] = histc(V,unique(V));
>> M = [V,N(X)]
M =
   6   3
   4   3
   4   3
   2   2
   9   2
   5   1
   1   2
   6   3
   2   2
   1   2
   6   3
   9   2
   4   3

[Adnan Habib]

Thanks but this one gives

"Error using histc

First Input must be a real non-sparse numeric array."

Answer 2

[darova]

Try this

a = randi(5,20,1);
x = a*0;
[a1,ix] = sort(a);              % sort array to see how many duplicates
k = 0;
for i = 1:length(a)-1
    if a1(i)~=a1(i+1)
        x(k+1:i) = i-k;         % write numer of duplicates
        k = i;                  % position of last diplicate
    end
end
x(k+1:end) = length(x)-k;       % write last portion of duplicates
[~,ix1] = sort(ix);             % restore original order
disp('sorted values with number of duplicates')
[a1 x]
disp('original values with numer of duplicates')
[a x(ix1)]

[Adnan Habib]

This one gives the error message as "Undefined operator '~=' for input arguments of type 'cell'."

I am very new to matlab and it is possible I did not provide some information regarding my data that might have been useful for you to help me out. Please let me know if you need any further information

[Walter Roberson]

You posted that you have a "vector"; it now appears that you have a cell array of some sort. Possibly it is a cell array of character vectors. Possibly it is a cell array of transfer functions. Possibly it is a cell array of function handles. We would need more information to advise you.

Answer 3

[Image Analyst]

Try this:

% Create sample data
v = randi(1000, 3079, 1)
% Now take a histogram:
edges = min(v) : 1 : max(v)+1;
hObject = histogram(v, edges) % Also displays the histogram
grid on;
% Create matrix with v as first column, and count as second column
m = [v, zeros(length(v), 1)];
% Assign the counts to each value.
for k = 1 : length(v)
	% Get the value of the vector at this index.
	value = v(k);
	% Get the counts from the histogram for that value
	% and stuff into the second column of m.
	m(k, 2) = hObject.Values(value);
end

[darova]

[Image Analyst]

darova, yeah, I know. But I didn't want to suppress the output because I thought he might want to see all the different kinds of things that the histogram object contains. Lots of useful stuff there. ?

Though I like/prefer Stephen's solution, but I'd use histcounts() instead of the deprecated histc() like he did.

[darova]

OK.

[Adnan Habib]

Thanks Image Analyst but your code gave this error message.

"Error using min

Invalid data type. First argument must be numeric or logical."

I am very new to matlab and it is possible I did not provide some information regarding my data that might have been useful for you to help me out. Please let me know if you need any further information

[Image Analyst]

I just copied and pasted my code and it ran fine. Moreover, the first argument to min() is a numeric vector -- it's a double. So you must have altered my code somehow. But you forgot to attach your modified script. Please do so if you want me to fix it.

[Adnan Habib]

I have actually done something else to bypass the requirement of counting. So I don't need this anymore. But I really do appreciate all your help. Thanks a lot.