CODE TOO SLOW AND SOMETIMES WONT RUN

i have made a code for motion detection in real time but its too slow and sometimes wont even run why?

here's my code :

clear all
clc

imaqmem(999999999);
threshold= 0.5;
frame=0;
video= videoinput('winvideo',1,'YUY2_1280x1024');  %creating video object
start(video)   %initiliazing video
first_frame = getsnapshot(video);
first_frame_gray=rgb2gray(first_frame);
[row,column,page]=size(first_frame);
dummy_matrix = zeros(row,column);
while(frame<50)
    current_frame=getsnapshot(video);
    current_frame_gray= rgb2gray(current_frame);
    frame_difference=imabsdiff(current_frame_gray,first_frame_gray);
    for nr=1:row                 
        for nc=1:column
            % if fr_diff > thresh then that pixel is in foreground       
            if ( (frame_difference(nr,nc) > threshold))  
                dummy_matrix(nr,nc) = frame_difference(nr,nc);
            else                
                 dummy_matrix(nr,nc) = 0;                 
            end              
        end
    end
    first_frame_gray=  current_frame_gray;
    subplot(2,1,1)
    imshow(current_frame)     
    subplot(2,1,2)
    imshow(uint8(dummy_matrix))
    frame=frame+1;
end
flushdata(video)  
delete(video)

Answer 1

[per isakson]

See:

• profile, Profile execution time for function
• Debugging, Diagnose problems with MATLAB® programs

The debugging tools of Matlab are good! Here are some links on debugging in Matlab

• Debugging in MATLAB
• Debugging session
• Debugging Approaches

Answer 2

[Image Analyst]

I do frame differencing in my demo. Run it and compare how it works to how yours works. The only difference is I get from frames from a video file instead of a camera, and I subtract the current frame from the average of several other frames instead of the latest one.