i need to use ifft on this (help plz im desperate)

Fs = 1000;                              
T = 1/Fs;                                
t = (0:L-1)*T; 
y1=110*sin(2*pi*50*t);
y2=10*sin(2*pi*250*t);
z=y1+y2;
f = Fs*(0:(L/2))/L;
z=abs(fft(z));
grid
plot(z)
figure(1);
semilogx(f,z(1:numel(f)))
d = designfilt('bandstopiir','FilterOrder',2, ...
             'HalfPowerFrequency1',49,'HalfPowerFrequency2',51, ...
             'DesignMethod','butter','SampleRate',Fs);
fvtool(d,'Fs',Fs)

[Adam]

So what is your question? That is just code, aiming doing something or other that you know and we don't.

[zayaz aya]

y1=110*sin(2*pi*50*t); y2=10*sin(2*pi*250*t);i have this 2 signal and adding it making 1 signal then making a time domain then perform fft on that the see the frequency domain on graphic then filtering it only lower than 50hz signal then perform ifft creating time domain and see it on graphic (sorry my english not that good need some sleep too)

[Adam]

So what is wrong exactly with using

doc ifft

just like you used fft?

[zayaz aya]

the thing is i dont know what im doing i tried ifft and its not working ifft should make everything back to where it was i think