idiots1.m

一些常被用于教学或者参考的概率论的实例的源代码

%idiots1.m/created by PJNahin for "Duelling Idiots"(7/3/98)
%This m-file simulates the original dueling idiots. The elements
%of the row vector duration are the number of duels of length k,
%i.e., duration(k)=# of duels that require k trigger-pulls to
%complete, where k=1,2,3,...
%
%
Duels=10000;           %total number of duels;
duration=zeros(1,60);  %assume no duel exceeds 60 trigger-pulls;
a=0;                   %number of times A has won, so far;
rand('state',100*sum(clock))  %new seed for generator
nd=0;                  %number of duels completed, so;
tp=0;                  %number of trigger pulls, so far, in present duel
while nd<Duels
   ra=rand;            %get two random numbers
   rb=rand;
   tp=tp+1;            %A pulls the trigger
   if (ra<=1/6)        %A wins
      duration(tp)=duration(tp)+1;   %duel is over, up-date the
                                     %duration vector;
      tp=0;            %initialize number of trigger-pulls for
                       %the next duel;
      a=a+1;
      nd=nd+1;
   else
      tp=tp+1;         %B pulls the trigger
      if (rb<=1/6)     %B wins
         duration(tp)=duration(tp)+1;   %duel is over, up-date the
                                        %duration vector;
         tp=0;                          %initialize the number of
                                        %trigger-pulls for the
                                        %next duel;
         nd=nd+1;
      end
   end
end                    %start next duel;
a=a/Duels;
disp(['The probability A wins is ',num2str(a)])
average=0;
for k=1:length(duration)
   average=average+k*duration(k);
end
average=average/Duels;
disp(['The average number of trigger-pulls/duel is 'num2str(average)])
bar(duration)          %plot a bar graph of the duration vector
title('Figure 2.1 - Relative Frequency of the Number of Trigger-Pulls per Duel')
xlabel('duration of duels, in units of trigger-pulls')
ylabel('number of duels')
figure(1)