GIF speed not as expected! Help!

Hello. I am trying to generate a GIF of a growing bar. However, the speed of the generating gif is really slow, and I don't understand how to make it faster. The 'DelayTime' is set to 0, and when the animation is generated in MATLAB is looks really fine. However, when I open the bar.gif, the animation is not fluid at all. This is the code

%draw rectangle and lambda
clear;
figure();
rectangle('Position',[0 2 10 1]);
axis off
set(gcf,'Position',[ -901   789   579    70])
t=0:0.05:3
l=1; a=0.5 
p=@(t,l,a) 1-(1-a).*exp(-l.*t); 
x=[0 0 10 10];
y=[2 3 3 2]; 
patch(x,y,'white');
frame=getframe(gca); im=frame2im(frame); 
[imind,cm] = rgb2ind(im,256); 
filename='bar.gif';
imwrite(imind,cm,filename,'gif','DelayTime',0.5, 'Loopcount',inf);

for tt=1:length(t)
    pt=p(t(tt),l,a);
    x=[0 0 10.*pt 10.*pt];
    patch(x,y,'green');
   % pause(.01); drawnow;

       frame(tt)=getframe(gca);
  end 
  for tt=1:length(t)

   im=frame2im(frame(tt)); 
       [imind,cm] = rgb2ind(im,256);
       imwrite(imind,cm,filename, 'gif','DelayTime',0,'WriteMode','append');
  end

[John D'Errico]

@DA Huang: Please don't answer a question with your own question. Use comments to make a comment.

Moved an answer by Da Huang into a comment:

"Have you solve this problem?"

Answer 1

[Utpal Kumar]

Edited and the delay time has been set to 0.1 seconds:

%draw rectangle and lambda
  clear;
  figure();
  rectangle('Position',[0 2 10 1]);
  axis off
  set(gcf,'Position',[ -901   789   579    70])
  t=0:0.05:3
  l=1; a=0.5 
  p=@(t,l,a) 1-(1-a).*exp(-l.*t); 
  x=[0 0 10 10];
  y=[2 3 3 2]; 
  patch(x,y,'white');
  frame=getframe(gca); im=frame2im(frame); 
  [imind,cm] = rgb2ind(im,256); 
  filename='bar.gif';
  imwrite(imind,cm,filename,'gif','DelayTime',0.1, 'Loopcount',inf);
  for tt=1:length(t)
      pt=p(t(tt),l,a);
      x=[0 0 10.*pt 10.*pt];
      patch(x,y,'green');
     % pause(.01); drawnow;
         frame(tt)=getframe(gca);
    end 
    for tt=1:length(t)
     im=frame2im(frame(tt)); 
         [imind,cm] = rgb2ind(im,256);
         imwrite(imind,cm,filename, 'gif','DelayTime',0.1,'WriteMode','append');
    end

[darova]

I just removed this line:

set(gcf,'Position',[ -901   789   579    70])

And it works ok for me

[Diptangshu Paul]

How is delaytime 0.1 faster than delaytime 0?

[DGM]

Short delay times depend entirely on the application to render them at the specified rate. It should be no surprise that at some point, the specified delay time fails to be met. While an exact zero delay time might seem a bit of a stretch, in practice it's worse than that. While most web browsers support delay times below 0.1s, most will treat 0 delay time as 0.1s. In other words, if you try to go too fast, you'll actually get slower results.

A number of people have surveyed this experimentally over the years. Here are two old ones that I found.

https://nullsleep.tumblr.com/post/16524517190/animated-gif-minimum-frame-delay-browser

https://www.deviantart.com/humpy77/journal/Frame-Delay-Times-for-Animated-GIFs-214150546

From the conclusion on the first link:

The first finding to note is that no modern browser surveyed supports frame delays below 0.02 seconds. Therefore, when creating an animated GIF, one should never use a frame delay below this threshold as it will be entirely ineffectual.

From the documentation for imwrite():

To achieve a high animation rate, set DelayTime to 0.02. Setting DelayTime to a lower value will slow down the actual animation rate in many image viewers and web browsers.