Fourier approximation of periodic function, plot not as expected.

I have made a periodic function and would like to plot a fourier approximation on the function I have plotted but am struggling to plot the fourier approximation. This is a normal sine wave which has been passed to a half wave rectifier. This is the fourier approximation below fN (t) = 1/π+1/2sin(t) −2/π cos(2nt)/4n^2 − 1

if true
M=1000;     %Data points
NCycle=5;   %5 cycles of wave
l=linspace(0,NCycle,M);
f=1/2/pi;   %Define frequency
Period=1/f; %Period is 1/frequency
sig=sin(2*pi*f*l*Period); %Orginal signal
subplot(211)              %Plot orginal signal
plot(sig);                %Plot
ax = gca;
ax.XTickLabel = [0,pi,2*pi,3*pi,4*pi,5*pi,6*pi,7*pi,8*pi,9*pi,10*pi];
grid                      %Grid on
for t=1:M                 %Start for loop time=1 to 1000   
if sin(2*pi*f*l(t)*Period)<=0   %If signal is less than or equals 0, next step
  sig(t)=0;                   %set to 0 if above true
else
  sig(t) = sin(2*pi*f*l(t)*Period); %If not less 0 plot sin(t)
end
end
  forapp = sig + 1/pi + 1/2*sin(t) - 2/pi *(cos(2*t)/(4-1));
subplot(212) 
plot(sig);
ylim ([-0.25 2.00])
ax = gca;
ax.XTickLabel = [0,pi,2*pi,3*pi,4*pi,5*pi,6*pi,7*pi,8*pi,9*pi,10*pi];
grid
figure;
plot(l,forapp);
  % code
end