'Electronic power measurement'

Power measurement in mathlab

clear;
f=50;
tmax=5/f;
Vmax=250;
Imax=10;
N=512;
tstep=1/(f*N);
t=tstep:tstep:tmax;
w=2*pi*f;
v=Vmax*sin(w*t);
il=Imax*sin(w*t);
p=v.*il;
a=[1 -2.99314850229460 2.98632045600046 -.99317191363767];
b=1e-006*[.1548 -.1347 -.1347 .1548];
y=filter(b,a,p);
energy=y.*t;
plot(t,p,'g');
hold on;
plot(t,y);
hold on;
plot(t,energy,'m');
legend('Instantaneous power','Chebysheb 3rd order low pass fitered');
xlabel('Time in second');
ylabel('Power in watts');
title('Electronic power measurement'