Summing FFT bins [closed]

What is the correct way to sum a range of frequencies in an FFT? I heard that I had to sum the squares after multiplying by the frequency.

Here's what I'm doing:

 freqDomain = abs(fft(signal.*window)); %FFT
freqDomain = freqDomain(2:(windowSize/2+1)); %We're only interested in the first half

freqDomain = freqDomain .* (1:windowSize/2); % Convert to PSD

lowFreq = freqDomain(lowFreqPeriod(2):lowFreqPeriod(1)); %Extract the range we need
highFreq = freqDomain(highFreqPeriod(2):highFreqPeriod(1));

lowFreq = sum(lowFreqDomain .^ 2); % sum of squares
highFreq = sum(highFreqDomain .^ 2);


The code works, and I'm getting what I think is a decent result, but is it mathmatically right?

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 Anon, I'm afraid MathOverflow is not for checking people's code. – S. Carnahan♦ Mar 24 2011 at 4:31 I only included the code to try and be helpful. I just wanted to know if it's correct to sum the squares of the fft bins. – Anon Mar 24 2011 at 12:06