How to calculate mean-square deviation?

I have the following code, which animates a particle. I need to figure out how to calculate the mean-square deviation within my code. So, I need to calculate the difference between (X1-X0)^2, (X2-X1)^2 and so on for each iteration. In the end, I need to average everything: ∑((X2-X1)^2)÷199. How do I incorporate this into my existing code?

     numMove = 200;
     x_List = zeros(numMove,1);
     y_List = zeros(numMove,1);
     % make fig. & start loop
     figure,
     for t = 2:numMove
     % add rand val between -1 and 1 to previous vals
     % save as new x & y coordinates
     x_List(t) = x_List(t-1) + 2*(rand()-0.3);
     y_List(t) = y_List(t-1) + 2*(rand()-0.3);

     %clear data currently on plot
     % animate particle
     cla 
     plot(x_List(1:t),y_List(1:t),'-r')
     plot(x_List(t),y_List(t),'ob','linewidth',8)
     axis([-20 20 -20 20]) 

     % particle speed
     pause(0.02)
     end

Answer 1

[Star Strider]

I’m not certain how ‘X0’, ‘X1’ and such relate to your code.

Here are a couple possibilities:

dxydt = diff([x_List, y_List]);                             % Take Differences Between Coonsecutive Values
mean_sqr_diff = mean(dxydt.^2);                             % Mean Of Squared Differences
mean_hypot = mean(hypot(x_List, y_List));                   % Mean Of Distances