function randwalk
tic
nn=0;
N=500:500:10000;
for j=N
    ra=0;
for i=1:30
    ra=ra+walk(i,j);
end
nn=nn+1;
mr(nn)=ra/30;%10´ÎÔËÐÐƽ¾ùÖµ
end
plot(N,mr,'ro')
toc
function rr=walk(x,n)
clc;close all;
z=0; % ÉèÖóõʼÊýÖµ£¬ÕâÀïÀûÓÃÒ»¸ö¸´ÊýÀ´±íʾλÖÃ
rand('state',x); % ³õʼ»¯Ëæ»úÊýµÄ״̬
%ph=plot(z);hold on; % »æͼ
T=1; % ¼ÆËãʱ¼äµÄ²ÎÊý
z1=1; % λÖõÄÖмä±äÁ¿
ti=title('time = 0','Fontsize',14,'Fontname','Times new roman'); % ÔÚͼÌ⴦ʵʱÏÔʾʱ¼ä
while T     [dx,dy]=choose_D(0.25,0.25,0.25,0.25); % Ëæ»úÉú³ÉÒ»¸öλÒÆÁ¿
    z1=z+[dx+i*dy]; % ¸üÐÂλÖÃÊýÖµ
   % plot(real([z,z1]),imag([z,z1])); % Á¬½Ótʱ¿ÌºÍt+1ʱ¿ÌÁ½µã»æÖÆÏ߶Î
    z=z1; % ¸üÐÂzµÄÊýÖµ
   % set(ti,'String',['time = ',num2str(T)]); % ¸üÐÂͼÌâ´¦µÄʱ¼äÊýÖµ
    T=T+1; % ʱ¼äÖµ¸üÐÂ
    %pause(0.01); % ÔÝͣһϣ¬ÏÔʾ¶¯»­Ð§¹û
end
rr=abs(z);
function [dx,dy]=choose_D(p1,p2,p3,p4);
% p1=0.2; % Ïò×óÔ˶¯µÄ¼¸ÂÊ
% p2=0.3; % ÏòÉÏÔ˶¯µÄ¼¸ÂÊ
% p3=0.1; % ÏòÓÒÔ˶¯µÄ¼¸ÂÊ
% p4=0.4; % ÏòÏÂÔ˶¯µÄ¼¸ÂÊ
r=rand; % ²úÉúÒ»¸öËæ»úÊý
if r     dx=-1; % x·½ÏòµÄËæ»úÒƶ¯Á¿
    dy=0; % y·½ÏòµÄËæ»úÒƶ¯Á¿
elseif r     dx=0; % x·½ÏòµÄËæ»úÒƶ¯Á¿
    dy=-1; % y·½ÏòµÄËæ»úÒƶ¯Á¿
elseif r     dx=1; % x·½ÏòµÄËæ»úÒƶ¯Á¿
    dy=0; % y·½ÏòµÄËæ»úÒƶ¯Á¿
else
    dx=0; % x·½ÏòµÄËæ»úÒƶ¯Á¿
    dy=1; % y·½ÏòµÄËæ»úÒƶ¯Á¿
end