MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn moreOpportunities for recent engineering grads.

Apply Today**New to MATLAB?**

Asked by Yogesh Shukla
on 25 Feb 2013

% Travellingsalesman problem

% Create random city distribution

n=20;

x=random('unif',-1,1,n,1);

y=random('unif',-1,1,n,1);

gam=1; mu=sign(x);

% End up where you start. Add starting point to end

x=[x' x(1)]';

y=[y' y(1)]';

mu=[mu' mu(1)]'; figure(1); hold off; g=plot(x,y,'.r');

set(g,'MarkerSize',20);

c0=cost(x,y,mu,gam); k=1; % Boltzmanconstant

nt=50; nr=200; % nt: temp steps. nr: city switches each T cp=zeros(nr,nt);

iran=inline('round(random(d,1.5001,n+0.4999))','d','n');

for i=1:nt

T=1.0 -(i-1)/nt

for j=1:nr

% switch two random cities

ic1=iran('unif',n); ic2=iran('unif',n);

xs=x(ic1); ys=y(ic1); ms=mu(ic1);

x(ic1)=x(ic2); y(ic1)=y(ic2); mu(ic1)=mu(ic2);

x(ic2)=xs; y(ic2)=ys; mu(ic2)=ms;

p=random('unif',0,1); c=cost(x,y,mu,gam);

if (c < c0 | p < exp(-(c-c0)/(k*T))) % accept

c0=c;

else % reject and switch back

xs=x(ic1); ys=y(ic1); ms=mu(ic1);

x(ic1)=x(ic2); y(ic1)=y(ic2); mu(ic1)=mu(ic2);

x(ic2)=xs; y(ic2)=ys; mu(ic2)=ms;

end

cp(j,i)=c0;

end

figure(2); plot(reshape(cp,nt*nr,1)); drawnow;

figure(1); hold off; g=plot(x,y,'.r'); set(g,'MarkerSize',20); hold on;

plot(x,y,'b'); g=plot(x(1),y(1),'.g'); set(g,'MarkerSize',30);

p=plot([0 0],[-1 1],'r--'); set(g,'LineWidth',2); drawnow;

end

Answer by Walter Roberson
on 25 Feb 2013

Accepted answer

That version of a random number routine is part of the Statistics Toolbox; see http://www.mathworks.com/help/stats/random.html

The Statistics Toolbox is optional extra cost for Academic and Professional licenses. It is, though, included in Student Version licenses, but the toolbox might not be installed by default.

Show 13 older comments

Walter Roberson
on 27 Feb 2013

What is the purpose of your line

p=rand(0,1);

rand(0,1) creates a 0 x 1 matrix of random numbers -- an empty matrix.

Yogesh Shukla
on 27 Feb 2013

I want to generate a random number between 0 and 1. Which function i can use?

Answer by Yogesh Shukla
on 26 Feb 2013

Edited by Yogesh Shukla
on 26 Feb 2013

Instead of using this routine (ie not using uniform distribution or random function) what else can I change in my code to eliminate errors and make code running. However if I use other function instead of 'random' then I get 'error using ==> ctranspose.. Transpose on ND array is not defined' in following lines:

x=[x' x(1)]';

y=[y' y(1)]';

mu=[mu' mu(1)]';

Thanks for your reply. Please help me because i have my presentation in few days.

## 2 Comments

## Walter Roberson

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/64840#comment_132133

If you describe some of the errors, people could help you debug it.

## Yogesh Shukla

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/64840#comment_132147

??? Undefined function or method 'random'

for input arguments of type 'char'.

Error in ==> salesman at 3

n=20; x=random('unif',-1,1,n,1);

y=random('unif',-1,1,n,1);