Matlab - Extracción aleatoria de los elementos de un vector

>> a=round(50*rand(1,15))

a =

    46    39    24    22    22    15    25    26    41    40    32    19    41    27    18

>> b=round(9*rand(1,10)+1); extracion=a(b)

extracion =

    41    41    15    25    15    24    22    22    24    41

>> b=round(9*rand(1,10)+1); extracion=a(b)

extracion =

    24    24    24    24    22    22    41    22    24    41

>> b=round(9*rand(1,10)+1); extracion=a(b)

extracion =

    40    22    39    24    22    15    24    15    25    24

>> b=round(9*rand(1,10)+1); extracion=a(b)

extracion =

    39    22    22    22    15    39    24    26    46    41

function [out]=random2(ini,fin,num)

% Choosse randomly a number (num) of elements from a vector [ini:fin]

% Randomly change the position of the vector. in pairs of twos

% 

% Imput:

% ini: Beginning of the vector

% fin: End of the vector

% nun: Number of elements to choose from the range of vector [ini:fin]

% 

% Output

% output vector

% 

%    contact:

%    Dave Correa 

%    correa.dave30@gmail.com

%    http://fismatlab.blogspot.com

%

% Example

% 

% [out]=random2(-20,20,10)

% 

% out =

%     -1     5    18    -3     1   -17    15     7     3    -6

% 

% [out]=random2(5,50,10)

% 

% out =

%     29    19    20    47    43    18    14    48    23    28

vr=ini:fin;             % Reference Vector

lon=fin-ini;            % variation or range of the vector

for nv=1:5*length(vr)   % vector length.

    p1=ceil(lon*rand);  % randomly chooses position to move. 

    p2=ceil(lon*rand);  % randomly selects the position where it is going to move.

    tp=vr(p1);          % temporal position.

    vr(p1)=vr(p2);      % Change inicial by end position.

    vr(p2)=tp;          % Change end by inicial position.

end

   out=vr(1:num);         % output vector

clear all

 trn_set=round(20*rand(7,5))

 n=size(trn_set,1);

 m=n;

i=1;

while i<=n

    seleccion=randi([1,n],1);

    trn_set1(i,:)=trn_set(seleccion,:);

    trn_set(seleccion,:)=[];

    n=size(trn_set,1);

    if i==round(m/2)

        break;

    end

    i=i+1;

end

 trn_set1

 trn_set2= trn_set

>> seleccion_aleatoria

trn_set =

     9     6     7    16    20

    17     3    18    20    11

    13     7     6    17    15

     7    15    12     2    17

     7    14     6     7     3

     5    14     3     5    18

    19     0     8     6     2

trn_set1 =

     5    14     3     5    18

     7    14     6     7     3

     7    15    12     2    17

     9     6     7    16    20

trn_set2 =

    17     3    18    20    11

    13     7     6    17    15

    19     0     8     6     2