Can any1 please explain me what does X= 0.01 : 0.01 : 2; and li=30/72 meant in ECG signal generation using Fourier series work done by R.KARTHIK sir. Iam new in MATLAB.Its very urgent.

x=0.01:0.01:2;
default=input('Press 1 if u want default ecg signal else press 2:\n'); 
if(default==1)
      li=30/72;  

        a_pwav=0.25;
        d_pwav=0.09;
        t_pwav=0.16;  

        a_qwav=0.025;
        d_qwav=0.066;
        t_qwav=0.166;

        a_qrswav=1.6;
        d_qrswav=0.11;

        a_swav=0.25;
        d_swav=0.066;
        t_swav=0.09;

        a_twav=0.35;
        d_twav=0.142;
        t_twav=0.2;

        a_uwav=0.035;
        d_uwav=0.0476;
        t_uwav=0.433;
  else
      rate=input('\n\nenter the heart beat rate :');
      li=30/rate;

      %p wave specifications
      fprintf('\n\np wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_pwav=0.25;
          d_pwav=0.09;
          t_pwav=0.16;
      else
         a_pwav=input('amplitude = ');
         d_pwav=input('duration = ');
         t_pwav=input('p-r interval = ');
         d=0;
      end    

      %q wave specifications
      fprintf('\n\nq wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_qwav=0.025;
          d_qwav=0.066;
          t_qwav=0.166;
      else
         a_qwav=input('amplitude = ');
         d_qwav=input('duration = ');
         t_qwav=0.166;
         d=0;
      end    

      %qrs wave specifications
      fprintf('\n\nqrs wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_qrswav=1.6;
          d_qrswav=0.11;
      else
         a_qrswav=input('amplitude = ');
         d_qrswav=input('duration = ');
         d=0;
      end    

      %s wave specifications
      fprintf('\n\ns wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_swav=0.25;
          d_swav=0.066;
          t_swav=0.09;
      else
         a_swav=input('amplitude = ');
         d_swav=input('duration = ');
         t_swav=0.09;
         d=0;
      end    

      %t wave specifications
      fprintf('\n\nt wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_twav=0.35;
          d_twav=0.142;
          t_twav=0.2;
      else
         a_twav=input('amplitude = ');
         d_twav=input('duration = ');
         t_twav=input('s-t interval = ');
         d=0;
      end    

      %u wave specifications
      fprintf('\n\nu wave specifications\n');
      d=input('Enter 1 for default specification else press 2: \n');
      if(d==1)
          a_uwav=0.035;
          d_uwav=0.0476;
          t_uwav=0.433;
      else
         a_uwav=input('amplitude = ');
         d_uwav=input('duration = ');
         t_uwav=0.433;
         d=0;
      end    

end

   pwav=p_wav(x,a_pwav,d_pwav,t_pwav,li);

   %qwav output
   qwav=q_wav(x,a_qwav,d_qwav,t_qwav,li);

   %qrswav output
   qrswav=qrs_wav(x,a_qrswav,d_qrswav,li);

   %swav output
   swav=s_wav(x,a_swav,d_swav,t_swav,li);

   %twav output
   twav=t_wav(x,a_twav,d_twav,t_twav,li);

   %uwav output
   uwav=u_wav(x,a_uwav,d_uwav,t_uwav,li);

   %ecg output
   ecg=pwav+qrswav+twav+swav+qwav+uwav;
   figure(1)
   plot(x,ecg);

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency

Answer 1

[Luuk van Oosten]

X= 0.01:0.01:2;

means X-values vary from 0.01 to 2 with a step size of 0.01. So you end up with X being 200 values equally spaced (with 0.01) in the range 0.01 and 2. My best guess is that this is your time window (or whatever values you have on your X-axis for your ECG).

li=30/72

means that the value specified as 'li' has the value of 30/72, commonly known as 0.4172. The 72 refers here to heartbeat (in rest, I guess). If your heartbeat goes up, li goes down and vice versa.

[Meha Gadkari]

OK sir i got it. But now my confusion is why only X axis is defined? why "y" axis is not defined? The li = 30/72 is not clear to me.

[Luuk van Oosten]

The values for your Y-axis are the 'ecg', which is defined as

ecg=pwav+qrswav+twav+swav+qwav+uwav

At the beginning of your script, you could choose to use some default settings to generate the ECG. Under this default settings, your li is 30/72. If you do not use the default settings, but something else, the li is calculated as follows:

   rate=input('\n\nenter the heart beat rate :');
      li=30/rate;

Which means that the li is dependent on the heart beat rate, which is called 'rate' (and by default is 72 beats/minute, which seems like a healthy normal heartbeat in rest).

You could choose to take another heartbeat rate. Let us say you want an ECG of a super excited heart beat with 150 heartbeats per minute....

rate = 150
li = 30/150

and this will subsequently influence your ECG.

[Meha Gadkari]

Thank you so much sir. From your answer i can conclude that "li" is the heart beat rate which could have any value. Now i only want to know what does "30" stands for? what is its significance?

[Walter Roberson]

You need to read the documentation that was provided as part of that File Exchange Submission as unfortunately there is no useful comments in the source.

[Meha Gadkari]

Sir, I gone through the file exchange.But I am unable to understand it