storing fft plot by some variable

nfft=1000; q= fftshift(fft(x,nfft)); n=length(q); fs=2560; fvals=fs*(-nfft/2:nfft/2-1)/nfft; figure, plot(abs(fvals), abs(q));

I am using this code to calculate FFT of signal x. FFT plot is represented between abs(fvals) and abs(q). I want to apply hilbert on this FFT plot. Now is it possible to represent that frequency sprectrum by only one variable so that I can use further function like Hil= Hilbert('one_variable') on that FFt signal. If it is possible or not please guide me something on it.