CODEWITHSUNDEEP
matlabvideoplot
jeff
jeff

Reputation: 13683

How to plot a real time signal in MATLAB?

I'm building a smile detection system, and I need to plot the probability of smile (from video input) like the graphs on the right in this video.

How can I do this in MATLAB?

Notes

I'm currently displaying the video frames with OpenCV & IntraFace default code, which looks something like this :

cf = 0; % Current Frame.
% create a figure to draw upon
S.fh = figure('units','pixels',...
              'position',[100 150 frame_w frame_h],...
              'menubar','none',...
              'name','Smile Detector',...              
              'numbertitle','off',...
              'resize','off',...
              'renderer','painters');

% create axes
S.ax = axes('units','pixels',...  
            'position',[1 1 frame_w frame_h],...
            'drawmode','fast');

set(S.fh,'KeyPressFcn',@pb_kpf);          

S.im_h = imshow(zeros(frame_h,frame_w,3,'uint8'));
hold on;
S.frame_h = text(50,frame_h-50,['Frame ' int2str(cf)] , 'fontsize', 15, 'Color' , 'c');

while true && ~stop_pressed
  tic;
  im = cap.read;  
  cf = cf + 1;        
  if isempty(im), 
    warning('EOF'); 
    break ;
  end

  set(S.im_h,'cdata',im); % update frame
  set(S.frame_h , 'string' ,['Frame ' int2str(cf)]);  
  do_something_with_frame(im);

  if isempty(output.pred) % if lost/no face, delete all drawings      
    if drawed, delete_handlers(); end
  else % face found       
    update_GUI(); 
  end
drawnow;
end

close;

end

And I want to add a live / moving graph like in the video. The graph will display a single value (a probability) between 0 and 1. And it should be updated with every new frame, therefore the plot should "flow" as the video flows.

What Have I Tried

I tried creating a new figure just like S in the code. But I cannot plot into it. I am also ok with adding the live graph in the same figure (S.fh), preferrably under the scene.

Upvotes: 1

Views: 1507

Answers (1)

QED
QED

Reputation: 808

Using linkdata and refreshdata will refresh a graph plot as you have new data.

    %some pretend data
    pX1 = rand;
    pX2 = 1-pX1;
    p = [pX1,pX2];
    bar(p)

    %link the data to the plot
    linkdata on

    for i=1:100
       pX1 = rand;
       pX2 = 1-pX1;
       p = [pX1,pX2];
       %refresh the linked data and draw
       refreshdata
       drawnow
    end

http://www.mathworks.co.uk/help/matlab/ref/linkdata.html

Hope it helps...

Upvotes: 1

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