% ### EXrandomWalk1D.m ### 11.15.14
% Calculates mean-squared distance for a group of independent 1-D random
% walkers, each moving with user-specified probablity of one step left vs right
% [Source (modified): Kevin Berwick (re 'Computational Physics', Giordano & Nakanishi)]
clear;
% -------------
N= 200; % Total # of (independent) walkers (each starts at x=0)
M= 100; % Total # of steps for each walker
K= 3; % # of walkers to show individual traces for [3]
bias= 0.5; % number between [0,1] to indicate bias for left vs right (0.5= equal prob.)
% -------------
% +++
step_number= zeros(1,M); %
x2ave= zeros(1,M); % allocate array to stored (suquentially averaged) MSD
step_number_array= [1:1:M]; %
% +++
%
% NOTE: the loop is set up in such a way to average x2ave across walkers
for r= 1:N
x=0; % initialize position for r'th walker
position(r,1)= 0;
% loop to go through M steps for r'th walker
for nn=1:M;
% conditional determines whether step is to the left or right
if (rand