Create vibration spectrum in the form of a waterfall plot for differential rolling element bearing

Hello,

I am being asked to create a vibration spectrum plot in the form of a waterfall plot as measured by a wireless accelerometer attached to the face of the outer race for a differential rolling element bearing based on an rpm vs time graph (defined below). My homework assignment previously asked that I calculate the bearing characteristic frequecies of Fundamental Train Frequency, Ball Spin Frequency, Ball Pass Frequency w/ respect to outer ring, and BPF w/ respect to inner ring, which was simple just plug and chug. My question now is how to use these frequencies to create a vibration spectrum using a waterfall plot.

time = linspace(0,43,43); %process time

thetaA = 0; %bearing contact angle

D = 180; %pitch diameter

d = 10; %ball diameter

n = 11; %number of balls in bearing

Nir = [linspace(0,11000,12) 11200 10000 8000 linspace(7600,7600,14) 8000 9000 10600 linspace(10000,0,11)]; %inner ring rpm

Nor = [linspace(0,4000,13) 3600 2660 linspace(2646,2646,14) 2660 3200 linspace(3800,0,12)] ; %outter ring rpm

%characteristic frequencies for theta = 0 deg

FTF_A = (1/120)*(Nor*(1+(d/D)*cos(thetaA))+Nir*(1-(d/D)*cos(thetaA))); %Fund Train Freq

BSF_A = (D/(120*d))*(1-(d/D)*cos(thetaA))*(1+(d/D)*cos(thetaA))*(abs(Nor+Nir)); % Ball Spin Freq

BPFI_A = (n/120)*(1+(d/D)*cos(thetaA))*(abs(Nor+Nir)); % BPF inner

BPFO_A = (n/120)*(1-(d/D)*cos(thetaA))*(abs(Nor+Nir)); % BPF outter

%plots the given info from the hw assignment: this is the rpm vs time graph

figure(3)

plot(time,Nir,'g',time,Nor,'b')

title('Bearing Operational Conditions')

xlabel('Time (min)')

ylabel('Rotational Speed (rpm)')

legend('Inner Race', 'Outer Race')

grid on