Error when running Motion History Image

Hi, I am newbie to matlab. Having error when running this code. Please help me.

function MHI = MHI3(fg)

% Initialize the output, MHI a.k.a. H(x,y,t,T)
MHI = fg;

% Define MHI parameter T
T = 15; % # of frames being considered; maximal value of MHI.

% Load the first frame
frame1 = fg{1};

% Get dimensions of the frames
[y_max, x_max] = size(frame1);

% Compute H(x,y,1,T) (the first MHI)
MHI{1} = fg{1} .* T;

% Start global loop for each frame
for frameIndex = 2:length(fg)

      %Load current frame from image cell
      frame = fg{frameIndex};

      % Begin looping through each point
      for y = 1:y_max
          for x = 1:x_max
              if (frame(y,x) == 255)
                  MHI{frameIndex}(y,x) = T;
              else
                  if (MHI{frameIndex-1}(y,x) > 1)
                      MHI{frameIndex}(y,x) = MHI{frameIndex-1}(y,x) - 1;
                  else
                      MHI{frameIndex}(y,x) = 0;
                  end
              end
          end
      end
  end

[junming liu]

I would like to take the liberty to ask you can get the source code of MHI.