How to obtain the Spectrogram of a signal I am trying to use Matlab to compute the spectrogram of a signal but I can't seem to figure out how Matlab computes the spectrogram.Consider the case where I have a signal x(t) with M samples and I want to compute it's spectrogram using hann windows of length N and using an overlap of K samples.

Because there are M samples and the advance time is (N - K) samples, I would expect the resultant spectrogram to have dimensions of either $N$ by $\frac{W}{(N - K)}$ OR if matlab only provides frequencies up to $\frac{f_s}{2}$ then dimensions to be $\frac{N}{2}$ by $\frac{W}{(N-K)}$ but I am getting weird dimensions.

The code below shows the case where I have computed the spectrogram when M = 32 * 700 = 24400, N = 256 and K = 256 - 32 = 224.

%specgram(data, ChunkSize, SampleRate, Size Of Hanning Window, Overlap (in Samples)  
    D = specgram( 1:1:(32*700),256, 8000 ,256 , 224);


produces a 129 * 693 matrix instead of the (256 * 700) or (128 * 700) spectrogram I was expecting.

Result should be an ($M$ by $\text{Number Of STFT Chuncks}$) matrix and 
$$
  \text{Number Of Chunks} = \frac{\text{Number Of Samples in Signal}}{\text{Advance Time (in Samples)}}
$$

$$
\text{Number Of Chunks} = \frac{32 * 700}{32} = 700
$$

Have I missed out on something? Any help will be appreciated.
Since the input signal is real, half of the FFT data is "useless" because it is simply the complex conjugate of the other half. More precisely, a 256-long FFT of a real signal will give you: the DC amplitude, 127 amplitudes, the amplitude at Nyquist, and 127 conjugate amplitudes.

Among the 700 chunks, 256 / 32 - 1 = 7 extend outside the boundaries of the original signal.

Hence, 129x693.