Can anyone please help me to understand the below mentioned code?

function [pwav]=p_wav(x,a_pwav,d_pwav,t_pwav,li)
l=li;
a=a_pwav;
x=x+t_pwav;
b=(2*l)/d_pwav;
n=100;
p1=1/l;
p2=0;
for i = 1:n
   harm1=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l);

function [qwav]=q_wav(x,a_qwav,d_qwav,t_qwav,li)
l=li;
x=x+t_qwav;
a=a_qwav;
b=(2*l)/d_qwav;
n=100;
q1=(a/(2*b))*(2-b);
q2=0;
for i = 1:n
    harm5=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);
    q2=q2+harm5;
end

qwav=-1*(q1+q2);

function [qrswav]=qrs_wav(x,a_qrswav,d_qrswav,li)
l=li;
a=a_qrswav;
b=(2*l)/d_qrswav;
n=100;
qrs1=(a/(2*b))*(2-b);
qrs2=0;
for i = 1:n
    harm=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);
    qrs2=qrs2+harm;
end

function [swav]=s_wav(x,a_swav,d_swav,t_swav,li)
l=li;
x=x-t_swav;
a=a_swav;
b=(2*l)/d_swav;
n=100;
s1=(a/(2*b))*(2-b);
s2=0;
for i = 1:n
    harm3=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);
    s2=s2+harm3;
end

swav=-1*(s1+s2);

function [twav]=t_wav(x,a_twav,d_twav,t_twav,li)
l=li;
a=a_twav;
x=x-t_twav-0.045;
b=(2*l)/d_twav;
n=100;
t1=1/l;
t2=0;
for i = 1:n
    harm2=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l);             
    t2=t2+harm2;
end

twav1=t1+t2;
twav=a*twav1;

qrswav=qrs1+qrs2;

             function [uwav]=u_wav(x,a_uwav,d_uwav,t_uwav,li)
  l=li;
  a=a_uwav
  x=x-t_uwav;
  b=(2*l)/d_uwav;
  n=100;
  u1=1/l
  u2=0
  for i = 1:n
      harm4=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l);             
      u2=u2+harm4;
  end

uwav1=u1+u2;
uwav=a*uwav1;

[James Tursa]

You need to format this to make it readable. But even then, it looks like there is too much going on for us to discern what the purpose of the code is without the help of any comments.

[Steven Lord]

Your best hope is probably going to be to ask the person from whom you obtained that code to explain it. [And ask them to add comments the next time they write code!]

[John D'Errico]

It is virtually impossible to understand what undocumented code is intended to do. We don't even know that it works as it should have. We have no indication of what the inputs are, nor what context the code is to be used under.

Contact the author. And tell them to write better code next time, AFTER they explain what it does.

[Meha Gadkari]

Actually I am working on ECG signal generation using Fourier series. So i obtained all the above mentioned data from MAT LAB file exchange. The name of author mentioned there is R.Karthik. As per my understanding, for the generation of ECG signal, the coding of P,QRS,T and U waveform is need to be paste on different scripts of MAT LAB.After that there is a complete bulk coding is need to be paste so that the ECG signal can be generated.In that coding, all of the P,QRS,T and U waveform are added together. As per my understanding, to generate the ECG signal this codes are used in order to define P,QRS ,T and U wave and they will not run as bcz when i tried to directly run the complete final file its was showing ample of errors..so i pasted all the coding of different waveforms on different scripts. So finally the ECG signal generated. I am again pasting below the code of P,QRS, T and U waveform one by one. I hope now you can help me :)

[Meha Gadkari]

function [pwav]=p_wav(x,a_pwav,d_pwav,t_pwav,li)

l=li;

a=a_pwav;

x=x+t_pwav;

b=(2*l)/d_pwav;

n=100;

p1=1/l;

p2=0;

for i = 1:n

      harm1=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l); 

      p2=p2+harm1;

end
pwav1=p1+p2;

pwav=a*pwav1;

[Meha Gadkari]

function [qwav]=q_wav(x,a_qwav,d_qwav,t_qwav,li)

l=li;

x=x+t_qwav;

a=a_qwav;

b=(2*l)/d_qwav;

n=100;

q1=(a/(2*b))*(2-b);

q2=0;

for i = 1:n

      harm5=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);

      q2=q2+harm5;

end

qwav=-1*(q1+q2);

[Meha Gadkari]

function [qrswav]=qrs_wav(x,a_qrswav,d_qrswav,li)

l=li;

a=a_qrswav;

b=(2*l)/d_qrswav;

n=100;

qrs1=(a/(2*b))*(2-b);

qrs2=0;

for i = 1:n

      harm=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);

      qrs2=qrs2+harm;

end

qrswav=qrs1+qrs2;

[Meha Gadkari]

function [swav]=s_wav(x,a_swav,d_swav,t_swav,li)

l=li;

x=x-t_swav;

a=a_swav;

b=(2*l)/d_swav;

n=100;

s1=(a/(2*b))*(2-b);

s2=0;

for i = 1:n

      harm3=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);

      s2=s2+harm3;

end

swav=-1*(s1+s2);

[Meha Gadkari]

function [twav]=t_wav(x,a_twav,d_twav,t_twav,li)

l=li;

a=a_twav;

x=x-t_twav-0.045;

b=(2*l)/d_twav;

n=100;

t1=1/l;

t2=0;

for i = 1:n

      harm2=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l);      

      t2=t2+harm2;
  end
  twav1=t1+t2;

twav=a*twav1;

[Meha Gadkari]

function [uwav]=u_wav(x,a_uwav,d_uwav,t_uwav,li)

l=li;

a=a_uwav

x=x-t_uwav;

b=(2*l)/d_uwav;

n=100;

u1=1/l

u2=0

for i = 1:n

      harm4=(((sin((pi/(2*b))*(b-(2*i))))/(b-(2*i))+(sin((pi/(2*b))*(b+(2*i))))/(b+(2*i)))*(2/pi))*cos((i*pi*x)/l);

      u2=u2+harm4;
  end

uwav1=u1+u2;

uwav=a*uwav1;

[Meha Gadkari]

All of the above mentioned codes are used to generate ECG signal using Fourier transform. I hope now anyone can help me to understand it

[John D'Errico]

Contact the author.

Answer 1

[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.

The contribution includes files ECG.doc and ECG.pdf which describe the mathematics involved.