Do you mean like this:
% Simulation of a random walk (delta = 1, tau = 1)
rng('Shuffle')
trials = 1000;
nSteps = 20;
positionArray = zeros(nSteps+1, 1);
stepNumber = 0:nSteps;
meansquaredisplacement = zeros(trials,1);
for trial = 1:trials
squareposn = 0;
position = 0;
for index = 1:nSteps
randomMove = rand; % random number between 0 and 1; used to decide direction of random move
if (randomMove <= 0.5)
position = position+1; % move right
else
position = position-1; % move left
end
end
squareposn = squareposn + position^2;
meansquaredisplacement(trial) = squareposn/nSteps;
end
plot(1:trials,meansquaredisplacement,'k') % plot the msd as a function of step number
set(gca,'FontSize',10);
xlabel('trial','FontSize',10)
ylabel('mean square displacement','FontSize',10)
