How can I get this markov code working?

I am trying to replicate this code however I always receive an error "not enough input arguments (Error in line 27: [r c]=size(T);). T is defined so is s0,n and V. Can anyone help?

 function [chain,state]=markov(T,n,s0,V);
  %function [chain,state]=markov(T,n,s0,V);
  %  chain generates a simulation from a Markov chain of dimension
  %  the size of T
  %
  %  T is transition matrix
  %  n is number of periods to simulate
  %  s0 is initial state
  %  V is the quantity corresponding to each state
  %  state is a matrix recording the number of the realized state at time t
  %
  %
  [r c]=size(T);
  if nargin == 1;
    V=[1:r];
    s0=1;
    n=100;
  end;
  if nargin == 2;
    V=[1:r];
    s0=1;
  end;
  if nargin == 3;
    V=[1:r];
  end;
  %
  %if r ~= c;
  %  disp('error using markov function');
  %  disp('transition matrix must be square');
  %  return;
  %end;
  %
  %for k=1:r;
  %  if sum(T(k,:)) ~= 1;
  %    disp('error using markov function')
  %    disp(['row ',num2str(k),' does not sum to one']);
  %    disp(['normalizing row ',num2str(k),'']);
  %    T(k,:)=T(k,:)/sum(T(k,:));
  %  end;
  %end;
  [v1 v2]=size(V);
  if v1 ~= 1 |v2 ~=r
    disp('error using markov function');
    disp(['state value vector V must be 1 x ',num2str(r),''])
    if v2 == 1 &v2 == r;
      disp('transposing state valuation vector');
      V=V';
    else;
      return;
    end;  
  end
  if s0 < 1 |s0 > r;
    disp(['initial state ',num2str(s0),' is out of range']);
    disp(['initial state defaulting to 1']);
    s0=1;
  end;
  %
  %T
  %rand('uniform');
  X=rand(n-1,1);
  s=zeros(r,1);
  s(s0)=1;
  cum=T*triu(ones(size(T)));
  %
  for k=1:length(X);
    state(:,k)=s;
    ppi=[0 s'*cum];
    s=((X(k)<=ppi(2:r+1)).*(X(k)>ppi(1:r)))';
  end;
  chain=V*state;

      if true
        % code
      end

[Dennis]

function works for me, how do you call it?

[Vanessa Kunzmann]

Whenever I call it with input variables it shows that state is not defined. When only calling the code, in line "[r c]=size(T);" occurs the error...

[Dennis]

does this work?

markov(randi(3,3,3),50,3,1:3)

[Vanessa Kunzmann]

it does work, however I receive this message:

error using markov function
row 1 does not sum to one
normalizing row 1
error using markov function
row 2 does not sum to one
normalizing row 2
error using markov function
row 3 does not sum to one
normalizing row 3

[Dennis]

In the code you have shown the line that produces that output is commented. Did your remove the % ?

And are the rows of T supposed to sum to 1? There might be a difference between no error message and working as intended.

[Vanessa Kunzmann]

Thanks for all the help! Removed the % but still cant get over the line [r c]=size(T);. And yes the Transition Probabilities have to sum up to one.

[Dennis]

Thats actually the first line of your function, and it does not work because it does not know T. Thats why i asked how you call markov function.

My best guess is that your are somehow trying to use markov() without passing parameters.