Count the number of occurances of an element using accumarray

Now I am trying to find the occurance of an element in a vector using

sum(dta(:,size(dta,2))==3);

How can accumarray be used to find the frequency of elements ?

A = [7 11 2 3 4 5 4 7 7 2 1 4 1];

How can I get a result such as,

• 7 3
• 11 1
• 2 2
• 3 1
• 4 2

and so on.

Thanks in Advance.

P.S: I looked through other threads, but did not understand how it worked. The example given was count = accumarray(A',1) and the result was a vector which was not clear to me.

Answer 1

[Azzi Abdelmalek]

A = [7 11 2 3 4 5 4 7 7 2 1 4 1] 
[a,b,c ]=unique(A,'stable')
out=[a' accumarray(c,1)]

[Azzi Abdelmalek]

look at edited code

[Ms. Mat]

what is this option 'stable'. I work with 2009 version. I dont have this option. Also could you please explain wat really the code is doing.

Thank You

[Azzi Abdelmalek]

A = [7 11 2 3 4 5 4 7 7 2 1 4 1] 
[a,b,c ]=unique(A) % you can remove 'stable' 
% a is the array containing unique value but in sorted order
%a=[ 1 2 3 4 5 7 11], if you remove 'stable', the result will be sorted
%c=[6 7 2 3 4 5 4 6 6 2 1 4 1] gives the indices of each value of A in a
% for example the 2nd value 11 in A is the 7nth in a 
out=[a' accumarray(c,1)], %the result is sorted

     1     2
     2     2
     3     1
     4     3
     5     1
     7     3
    11     1

Answer 2

[Sean de Wolski]

I would use histc on the output vector c that you have above from unique()

Frankly you should be able to skip all of that altogether:

[uv, idx] = unique(A);
n = histc(A,uv);
nA = n(idx)

(not tested in ML)