# Plotting a time series e^(-at) cos⁡((bt) u_s (t)) for two cases, first for a=3 and b=50, then for a=-3 and b=50.

2 views (last 30 days)
Christi Kruger on 29 Sep 2023
Commented: Dyuman Joshi on 30 Sep 2023
I have been trying to plot the time series (e^(-at)*cos(bt)*u_s(t))) for two cases, first for a=3 and b=50, then for a=-3 and b=50 . Plot both cases on the same plot. Let the vertical axis span from -6 to 6 and the horizontal axis from 0 to 1 seconds.
a1=3;
b1=50;
a2 = -3;
b2= 50;
f1 = exp^(-a1*t)*cos(b1*t)*u(t);
f2 = exp^(-a2*t)*cos(b2*t)*u(t);
ts1 = timeseries (f1,0:1);
ts2 = timeseries(f2,0:1);
ts1.Name = 'time series';
ylim(-6:6);
plot(ts1);
hold on
plot(ts2);
Torsten on 29 Sep 2023
What is u(t) ?
Dyuman Joshi on 30 Sep 2023
An error occurs in this line -
ylim(-6:6);
This is not how ylim works.
From the documentation - "Specify limits as a two-element vector of the form [ymin ymax], where ymax is greater than ymin."
And you don't need to define the variables as timeseries object. Plot directly, as has been show below.
You can also use fplot

KSSV on 30 Sep 2023
clc; clear ;
a1=3;
b1=50;
a2 = -3;
b2= 50;
t = linspace(0,1) ;
f1 = exp(-a1*t).*cos(b1*t) ;
f2 = exp(-a2*t).*cos(b2*t);
plot(t,f1,'r');
hold on
plot(t,f2,'b');
ylim([-6 6])
legend('f1','f2')