Most frequent element in array

Hello

Is there any matlab function for calculating directly the most
frequent element/value in an array? (or preferably, in a sparse
matrix). I'm stuck here and fed up with histograms.

Thanks in advance

help hist

"Nuno Benavente" <nuno.benavente@ist.utl.pt> wrote in message
news:ef04910.-1@webx.raydaftYaTP...
> Hello
>
> Is there any matlab function for calculating directly the most
> frequent element/value in an array? (or preferably, in a sparse
> matrix). I'm stuck here and fed up with histograms.
>
> Thanks in advance

Nuno Benavente wrote:
>
>
> Hello
>
> Is there any matlab function for calculating directly the most
> frequent element/value in an array? (or preferably, in a sparse
> matrix). I'm stuck here and fed up with histograms.
>
> Thanks in advance

How come, you ar fed up with histograms?

What kind of elements are there in your array. Not floating point
numbers, I hope.

/ per

sort and unique in combination will do the job!
BR
Anders
"Nuno Benavente" <nuno.benavente@ist.utl.pt> skrev i meddelandet
news:ef04910.-1@webx.raydaftYaTP...
> Hello
>
> Is there any matlab function for calculating directly the most
> frequent element/value in an array? (or preferably, in a sparse
> matrix). I'm stuck here and fed up with histograms.
>
> Thanks in advance

In article <dOSce.52547$Of5.33494@nntpserver.swip.net>, "Anders Björk"
<huanbj@hotmail.com> wrote:

> sort and unique in combination will do the job!
> BR
> Anders
> "Nuno Benavente" <nuno.benavente@ist.utl.pt> skrev i meddelandet
> news:ef04910.-1@webx.raydaftYaTP... 
------
Hello Nuno, I think 'histc' is the way to go but you have to set up its
"edges" parameter properly.  Using Anders' idea for 'unique', try this:

y = unique(x);
n = histc(x,y); % Use the unique values as edges
[f,i] = max(n);
mf = y(i); % mf is most frequent element of x & it occurs f times

Note Per's warning!  This will only group element values together that are
exactly equal.  If you want some tolerance in your "equality", you have a
different problem.

(Remove "xyzzy" and ".invalid" to send me email.)
Roger Stafford

Thank you for your replies!

Roger, your solution worked perfectly! Thank you so much :)

Roger Stafford:
<SNIP OP wants most frequent element...

y=unique(x);
n=histc(x,y);
[f,i]=max(n);
mf=y(i);

another solution for this particular problem (we don't really need
the overhead of <unique> )

% the data
clear all; % save old stuff!
n=pi*[10 10 10 12 4 4 2 2 2 2 2 2].';
n(end-2:end)=n(end-2:end)+5*eps;
% the engine
ns=sort(n); % only part of <unique>
c=histc(ns,ns);
r=ns(c==max(c));
% the result
format long g;
[r r-2*pi]

just a thought
us

us wrote:
> Roger Stafford:
> <SNIP OP wants most frequent element...
>
>      y=unique(x);
>      n=histc(x,y);
>      [f,i]=max(n);
>      mf=y(i);
>
> another solution for this particular problem (we don't really need
> the overhead of <unique> )
>
> % the data
>      clear all; % save old stuff!
>      n=pi*[10 10 10 12 4 4 2 2 2 2 2 2].';
>      n(end-2:end)=n(end-2:end)+5*eps;
> % the engine
>      ns=sort(n); % only part of <unique>
>      c=histc(ns,ns);
>      r=ns(c==max(c));
> % the result
>      format long g;
>      [r r-2*pi]
>
> just a thought
> us

% how about a solution that doesn't use histogram ?
n=pi*[10 10 10 12 4 4 2 2 2 2 2 2].';   % test dataset provided by us
n(end-2:end)=n(end-2:end)+5*eps;        % try with or without this stmt
n1=sort(n);         % collect like values together
n2=diff(n1)==0;     % n2=0 at change of value
% want longest string of 1's
n3=double(n2);      % n2=logical, need double
n4=find(n2==0);
n3(n4)= 1-diff([0;n4]); % this will cancel out running sum
n5=cumsum(n3);      % longest string of 1's will give max value
result=n1(n5==max(n5)); % following us get all values
[result result-2*pi]

Regards,
-rajeev-

<SNIP mode discussion>
Note for the record that Michael Robbins posted to the FEX a nice
little wrapper (mode.m) for this.
Brett

Brett Shoelson wrote:
> <SNIP mode discussion>
> Note for the record that Michael Robbins posted to the FEX a nice
> little wrapper (mode.m) for this.
> Brett

Thanks for bringing this to my attention.  Also for the record, on the
File Exchange I found

4/24/04  David Li's function (hist with integer bins)
6/16/04  Michael Robbins' mode function (unique+hist)
11/17/04  Harold Bien's suggestion in response to Michael's post
(unique+diff: no hist)

Regards,
-rajeev-