function?[indscidx]?=?kmedoids（Dk）
%?[indscidx]?=?kmedioids（Dk）
%
%?Performs?k-mediods?clustering;?only?requires?a?distance?matrix?D?and
%?number?of?clusters?k.??Finds?cluster?assignments?“inds“?to?minimize?the
%?following?cost?function:?

%?sum（D（inds==iinds==i）2）?summed?over?i=1:k?
????
%?Determining?cluster?assignments?and?cluster?centers?are?both?done?in?an
%?efficient?vectorized?way.??Cluster?assignment?is?O（nk）?and?cluster
%?centering?is?O（k*（max?cluster?size）^2）
%
%?INPUTS
%?D:?nxn?all-pairs?distance?matrix
%?k:?number?of?clusters
%
%?OUTPUTS
%?inds:?nx1?vector?of?assignments?of?each?sample?to?a?cluster?id
%?cidx:?kx1?vector?of?sample?indices?which?make?up?the?cluster?centers
%
%?DEMO
%?Run?with?no?arguments?for?demo?with?2d?points?sampled?from?3?gaussians
%?using?the?gmdistribution?function?from?the?stats?toolbox

%?Written?by?Ben?Sapp?September?2010
%?benjamin.sapp@gmail.com

if?nargin?==?0
????demo（）;
????return;
end

n?=?size（D1）;

%?randomly?assign?centers:
cidx?=?randperm（n）;
cidx?=?sort（cidx（1:k））;

iter?=?0;
while?1
????inds?=?assign_pts_to_clusters（Dcidx）;
????[cidxenergy_next]?=?update_centers（Dindscidxk）;
????
????if?iter>0?&&?energy_next?==?energy?
????????break;
????end
????energy?=?energy_next;
????
????fprintf（‘iter:?%04d?energy:?%.02f\n‘iterenergy）
????iter?=?iter+1;
end

function?inds?=?assign_pts_to_clusters（Dcidx）
S??=?D（cidx:）;
[valsinds]?=?min（S[]1）;

function?[cidxenergy]?=?update_centers（Dindscidxk）
energy_next?=?nan（k1）;
for?i=1:k
???indsi?=?find（inds==i）;
???[energy_next（i）minind]?=?min（sum（D（indsiindsi）2））;
???cidx（i）?=?indsi（minind）;
end

energy?=?sum（energy_next）;


function?demo（）
%?problem?params
k?=?3;
n?=?2000;
MU?=?[1?2;-1?-2;?3?0];
SIGMA?=?cat（3[2?0;0?.5][1?0;0?1]?eye（2））;
p?=?ones（13）/3;
obj?=?gmdistribution（MUSIGMAp）;
pts?=?random（objn）‘;

%form?all-pairs?distance?matrix?in?an?efficient?way
X?=?pts‘;
temp?=?sum（X.^22）;
X=sqrt（2）*X;
D=-X*X‘;
D=bsxfun（@plusDtemp）;
D=bsxfun（@plusDtemp‘）;

%run?kmedioids
[indscidx]?=?kmedioids（Dk）;

%display
clf?hold?on?axis?square
c?=?lines（k）;
for?i=1:k
????ptsi?=?pts（:inds==i）;
????ctrpt?=?pts（:cidx（i））;
????plot（ptsi（1:）ptsi（2:）‘.‘‘color‘c（i:））
????plot（ctrpt（1）ctrpt（2）‘kx‘‘markersize‘22‘linewidth‘6）????
end

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????文件????????2289??2014-04-23?02:13??kmedoids\kmedoids.m
?????目錄???????????0??2014-04-27?04:14??kmedoids\