MATLAB - How do I get the Filter Function to get the output Energy Spectrum?
What u plotted is the complex fft samples.  In order to see the psd in matlab use plot([-1/2:1/ffteln:1/2-1/fftlen]*fs, 10*log10( abs( fftout)./length(fftout)).^2)).  I am assuming of coarse that your signal is real and therefore plotting from -fs/2:fs/2 is standard practice.  For complex signals usually you want to plot from 0:Fs because nyquist is Fs for complex.