plotting histogram for frequency versus amplitude

Hi Volks, I have a question regarding Histogram. I am plotting a graph, which is frequency versus amplitude. On the frequency axes, I have amplitude of 10 signals. Now I need to plot a histogram which shows how much fluctuations do i have at paricular frequency for all 10 signals. For example, at 90KHz, how much fluctiating the amplitude of all 10 signals. How to do histogram in this case.

    figure,plot(f2,abs(amp));
    xlabel('Frequency in KHz');ylabel('amp');