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Re: two questions -- one answer


From: Doug Stewart
Subject: Re: two questions -- one answer
Date: Sun, 11 Sep 2005 17:45:09 -0500
User-agent: Mozilla Thunderbird 1.0 (Windows/20041206)

address@hidden wrote:

Hello!

I've just installed octave (cygwin) to my computer and now learning the 
difference between octave and matlab.
I can find the solution for the followings on my own. Please help me and sorry 
for the supposingly stupid questions.

1. dir command does not work:
octave:15> dir
usage: dir (file)
error: evaluating if command near line 53, column 3
error: called from `dir' in file 
`/usr/share/octave/2.1.71/m/miscellaneous/dir.m'

??? What can be wrong?

2. In one of my mfiles the plot command does not work. Why? I copied the short m file to the end of this mail. The graphs are not showed, no error reports, no any messages at all but plot command works pretty well in another mfile with the same syntax. So I really have no any idea what could happen. All things that happen is something like that:

octave:19> mine

MINE MANAGEMENT MODEL
octave:20>



thanks in advance

Klári

===============================mine.m=======================================
% Mine Management Model
 fprintf('\nMINE MANAGEMENT MODEL\n')
%  close all

% Enter algorithm parameters
 maxit = 100;
 tol = sqrt(eps);
% Enter model parameters
 price = 1;                    % price of ore
 sbar  = 10;                  % initial ore stock
delta = 0.9; % discount factor
% Construct state and action spaces
 S = (0:sbar)';                % vector of states
 X = (0:sbar)';                % vector of actions
 n = length(S);                % number of states
 m = length(X);                % number of actions


% Construct reward function (f) and state transition function (g)
% Vectorized version
 [SS,XX] = gridmake(S,X);
 f = (price-XX./(1+SS)).*XX;
 f(XX>SS) = -inf;
 f = reshape(f,n,m);
 g = getindex(SS-XX,SS);
 g = reshape(g,n,m);
 clear SS XX
P = sparse(1:n*m,g(:),1,n*m,n);

% policy iteration
v = zeros(n, 1);
for it=1:maxit
        vold = v;
        [v, x] = valmax(v, f, P, delta);
        if norm(v-vold)< tol
                return;
        end
end     

% Plot optimal value function
 figure(1);
 plot(S,v,';;',)
 title('Optimal Value Function');
 xlabel('Stock'); ylabel('Value');


 % Plot optimal policy function
 figure(2);
 plot(S,X(x))
 title('Optimal Extraction Policy');
 xlabel('Stock'); ylabel('Extraction');








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The plot command automatically starts up GNUPLOT and sends the info to it through a pipe.

If after you have drawn a plot you then close GNUPLOT and try to plot another plot it will act like you have reported. So the solution is to leave GNUPLOT there and let octave handle GNUPLOT.

If you have shut down GNUPLOT then you must restart Octave to get it back again.
Doug




-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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