# Varying a sinusoidal input

1 view (last 30 days)
Reuben Salisbury on 13 Apr 2020
Commented: Reuben Salisbury on 14 Apr 2020
I am trying to create a sinusoidal model to simulate the sea as a fixed surface, but I'm not sure how to adapt a simple sinusoidal model so that the wave height and frequency varies within a range (more like the sea). I would change the range for varying sea states, but just need to see how to create a varying amplitude and frequency within a secified range.
Reuben Salisbury on 13 Apr 2020
I am trying to make the value of X0 vary so that the maximum amplitude is not always constant
darova on 13 Apr 2020
x = 0:0.01:10;
y = sin(20*x).*sin(x);
plot(x,y)

Ameer Hamza on 13 Apr 2020
Edited: Ameer Hamza on 13 Apr 2020
Try something like this
t = linspace(-10,10,100);
[X,Y] = meshgrid(t);
f = (sin(X+Y)/2+0.5)*0.3+0.3; % frequency change between 0.3 to 0.6
A = (cos(X.*Y/3.5)/2+0.5)*0.3 + 0.7; % amplitude change between 0.7 to 1.0
Z = A.*sin(f.*X).*sin(f.*Y);
surf(X,Y,Z)
It have both variable frequency and amplitude between a specified range.
Ameer Hamza on 14 Apr 2020
In this equation
fd = (sin(x)/2+0.5)*0.4+0; % frequency change between 0 to 0.4
0 at the end is the lower range of the frequency and 0.4 is the change in frequency. So
fd = (sin(x)/2+0.5)*1.0+0.5;
will have frequency in range [0.5, 1.5].
Similar parameters are defined for amplitude.
Reuben Salisbury on 14 Apr 2020
Great, thanks again.