I perform FFT-IFFT in order to take out 50 Hz and its harmonics from my signal, using Matlab.
For this purpose I break down my signal into windows of 1024 samples, and perform FFT on it. I do overlapping of 50% as well. After FFT is done, I take out those harmonics, and do IFFT in order to get filtered data. 
My question is:
How to sum up all those windows with overlaps to get a signal?

my code is below. As you can see, I perform FFT-IFFT on each window and do not know how to get all windows back together.

```
[y, Fs, nbits] = wavread([fileName]);                    %read the data
[noSamples, noChannels] = size(y);
N = 1024;                                                 %window length 2^10
winLength=N; 
Fres = Fs/N;                                              % resolution frequency
nofWins = floor(noSamples/winLength);                     % No of full windows
noWins = round((100/50)*nofWins - 1);                     % rounded no of windows
yPaddedLength = floor(noWins*0.5*winLength + winLength);  % padding wth 0
yZeroPadded =[y zeros(1, (yPaddedLength - noSamples))];   % padded signal y
nofWinsPadded = round(yPaddedLength/winLength);
noWinsPadded = round((100/50)*nofWinsPadded - 1);         % no of padded windows

odd = true;
for k = 1:(noWinsPadded-1)
    j = floor(0.5*k);
    at = j*winLength + 1;
    overlapWinLength=floor(0.5*winLength);
    range = at:(at + winLength - 1);

if odd
    data = yZeroPadded(range, 1);
    data_sum=sum(data);                                    % from now on - to perform 
                                                           % DC removal
    data_average=data_sum/N;
    data=data-data_average;

else
   data = yZeroPadded(range+overlapWinLength, 1);
    data_sum=sum(data);
    data_average=data_sum/N;
    data=data-data_average;
end;

odd=~odd;
    spectrum = fft(data);
    F=length(spectrum);
    F=spectrum;
    F(10:11)=zeros;                         % FFT No equals to zero removes harmonics
    F(17:18)=zeros                          % and so on
filtered_signal=IFFT(F);

```

Thanking you in anticipation,
Elen Che