Need a little help on my Spectrum Analyzer. It's pretty much done but I'm stuck.

[irrelevant]

Hi, I'm new to MatLab and I'm trying to build a spectrum analyzer. I think I have most of it but I can't get it to work. I was hoping someone could glance at it to see if it was something obvious. Thanks for any help.

The script is at the bottom

This is the function:


function y = CPetty_spectrumAnalyzer( filename, winLength, overlapLength, window, fftlength)

%Input
%filename: name of .WAV file to be analyzed
%winLength: length of signal window (in samples)
%overlapLength: length of signal overlap (in samples)
%window: window type: passes one of the following strings
% ‘rect’
% ‘hamming’
% ‘hann’
% ‘blackman’
% ‘bartlett’
%fftlength: number of samples to be used in fft (default: winLength)
%Output
%y : a 2D matrix containing the normalized magnitudes of the STFT in dB

%If the user did not input 5 arguments total...
if (nargin ~= 5);
disp('You have to enter 5 arguments (filename,winLength,overlapLength,window,fftlength')
end

%If the user trys to name the file with numbers and symbols
if ~isstr(filename)
error('The filename has to be letters with single quotes around it')
end

%If the overlap value is greater than the window length.
if (overlapLength > winLength)
error('The overlap value cant be longer than the window length')
end

%Since the fftlength uses the samples in the windows, it can't be less
%than the window length.
if fftlength < winLength,
error('The fftlength cant be less than the winLength')
end

if (winLength < 1), abs(winLength);
disp('You cant use negative numbers, I made them positive for you')
end

if (overlapLength < 1), abs(overlapLength);
disp('You cant use negative numbers, I made them positive for you')
end

if (fftlength < 1), abs(fftlength);
disp('You cant use negative numbers, I made them positive for you')
end


if (mod(winLength, 1) ~= 0)||(mod(overlapLength, 1) ~= 0)||(mod(fftlength, 1) ~= 0);
disp('Lengths cant be floating points. I rounded them up to the next integer')
end


switch window
case 'rect'
win = rect(winLength);
case 'hamming'
win = hamming(winLength);
case 'hann'
win = hann(winLength);
case 'blackman'
win = blackman(winLength);
case 'bartlett'
win = bartlett(winLength);
otherwise
error('rect, hamming, hann, blackman or bartlett');
end

%Load the file and store the audio in x and the samplerate in fs.
[x, fs] = wavread(filename);

%To make a stereo file mono, the mean is calculated.
x = mean(x, 2);

%Make the hop size the difference between the window and overlap lengths.
hop = winLength - overlapLength;

%To buffer the signal to the right window and overlap lengths.
buf = buffer(x, winLength, overlapLength);

%K is the number of frames that are needed for the function.
K = ceil(length(x)/hop);

%To create a matrix by tiling.
winMat = repmat(win, 1, K);

%Matrix multiplication for each frame of audio by each window function.
winBuf = buf .* winMat;

%FFT of the windowed signal.
fftBuf = fft(winBuf, fftlength);

%Find the normalized magnitudes of the post STFT signal in Db.
magnitudes = 20*log10(abs(fftBuf) / (fftlength/2));

%Find the ammount of information that's in the bin.
NyqBin = (length(magnitudes)/2) + 1;

end
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

y = CPetty_spectrumAnalyzer('testSig.wav', 1024, 512, 'hann');

[x, fs] = wavread('testSig.wav');

dur = length(x) / fs;

time = linspace( 0, dur, size(y, 2) );

freqs = linspace( 0, fs/2, size(y,1)+1 );

imagesc(time, freqs, y);
axis( 'xy' )
xlabel('Time (s)');
ylabel('Frequency (Hz)');
title('Spectogram');
colormap('Autumn')

f = figure;
movegui(f,'center');

imagesc(time, freqs, y);
axis( 'xy' ) %Flip axes
xlabel('Time (s)');
ylabel('Frequency (Hz)');
ylim([0 8000]); % Limit y axis to 8kHz
title('Spectogram result for 0 - 8kHz.')
colormap('Autumn');