Choosse randomly number of elements from a vector

Choosse randomly a number of elements from a vector. Randomly change the position of the vector

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
%
% 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

% contact:
% Dave Correa
% [e-mail]
% http://fismatlab.blogspot.com