Need help with GUI axes and arduino

So I'm planning on making an Matlab interface with Arduino UnoR3 and got confused with the axes (graph as you may). I referred some sources and got this code going as wanted. However, I wonder if I should put this on "push_button_callback" or somewhere else (if so, where should I put it); further, as the plot scrolling, I find that the previous part of the graph is lost, how can I recall that part, or I should just plot another figure manually?

P/s: this is just a demo with assigned data

Many thanks

clear;
clc;

%User Defined Properties 
plotTitle = 'Serial Data Log';  % plot title
xLabel = 'Elapsed Time (s)';    % x-axis label
yLabel = 'Data';                % y-axis label
plotGrid = 'on';                % 'off' to turn off grid
min = 0;                     % set y-min
max = 150;                      % set y-max
scrollWidth = 50;               % display period in plot, plot entire data log if <= 0
delay = .5;                    % make sure sample faster than resolution
dat=randi(100,1,200);
%Define Function Variables
time = 0;
data = 0;
i=0;
%Set up Plot
plotGraph = plot(time,data);

title(plotTitle,'FontSize',25);
xlabel(xLabel,'FontSize',15);
ylabel(yLabel,'FontSize',15);
axis([0 10 min max]);
grid(plotGrid);

tic

while ((ishandle(plotGraph) && i<length(dat)))%Loop when Plot is Active

      if(~isempty(dat) && isfloat(dat)) %Make sure Data Type is Correct        
          i = i + 1;    
          time(i) = i*0.5;    %Extract Elapsed Time
          data(i) = dat(i); %Extract 1st Data Element  

          %Set Axis according to Scroll Width
          if(scrollWidth > 0)
          set(plotGraph,'XData',time(time > time(i)-scrollWidth),'YData',data(time > time(i)-scrollWidth));
          %plot(time(time > time(count)-scrollWidth),data3(time > time(count)-scrollWidth));
          axis([time(i)-scrollWidth time(i) min max]);
          %set(plotGraph,'XData',time(time > time(count)-scrollWidth),'YData',data3(time > time(count)-scrollWidth));
          %axis([time(count)-scrollWidth time(count) min max]);
          else
          set(plotGraph,'XData',time,'YData',data);
          axis([0 time(i) min max]);
          end

          %Allow MATLAB to Update Plot
          pause(delay);
      end
  end

%Close Serial COM Port and Delete useless Variables
clear count dat delay max min baudRate plotGraph plotGrid plotTitle s ...
        scrollWidth serialPort xLabel yLabel;

      end

Answer 1

[Viet Le]

Update, I have modified some lines to suit my purpose. However, there are lines confused me.

I.e if I do it like below, the code runs smoothly

          if(i<(scrollWidth/delay))
          set(plotGraph,'XData',time,'YData',data);
          axis([0 scrollWidth min max]);
          else
          set(plotGraph,'XData',time,'YData',data);
          axis([time(i)-scrollWidth time(i) min max]);
          end

If I do it like this

if(i<(scrollWidth/delay))
          set(plotGraph,'XData',time,'YData',data);
          axis([0 scrollWidth min max]);
          else
          set(plotGraph,'XData',time,'YData',data);
          axis([time(i -(scrollWidth/delay)) time(i) min max]);
         %time(i-(scrollWidth/delay)) = time(i)-delay
          end

then the code stop at i = scrollWidth/delay (in this case, i=100). Can someone explain my problem? I suppose Matlab can access previous values of time(i) while in a loop, but it doesnt make sense to me. Many thanks