how to plot a continuous signal

I want to plot x(t) = cos(200*pi*t*u(t)) and define u(t) seprately and then plot x(-t),x(t/3)

i wrote this

x = @(t) cos(200*pi*t*u(t));

t = linspace(-1, 1);

figure(1)

plot(t, x(t))

grid

function y = u(x)

y=0;

if x>=0

y=1;

end

end

Answer 1

[Star Strider]

This should get you started:

u = @(t) t>=0;
x = @(t,u) cos(200*pi*t.*u(t));
t = linspace(-1, 1);
figure(1)
plot(t, x(t,u))
grid

Extending that:

u = @(t) t>=0;
x = @(t,u) cos(200*pi*t.*u(t));
t = linspace(-1, 1);
figure(1)
plot(t, x(t,u))
hold on
plot(t, x(-t,u))
plot(t, x(t/3,u))
hold off
grid

Experiment to get different results.

[Mohammadreza kalantari]

thanks a lot

whats about 1/x(t,u) & x(1/t,u)

I think the eror is devided by zero

how can i solve it?

[Star Strider]

My pleasure.

Add: 1E-14 (or some similar small value) to whatever is in the denominator. That will still result in a very large number, however not Inf or NaN.

Note that in those instances, you need to use element-wise division, ./. See the documentation section on Array vs. Matrix Operations for a fulll discussion.

[Mohammadreza kalantari]

ok

now i want to plot A*exp(j*2*pi*t)

which A is a constant variable and j is an imaginary unit

[Star Strider]

Try this:

A = 42;                                                 % Universal Answer (HHGTTG)
y = @(t) A*exp(1j*2*pi*t)
t = linspace(-1, 1);

figure
plot(t, real(y(t)),'-b',    t, imag(y(t)), '--')
grid
legend('\Re', '\Im')

Experiment to get the result you want.

[Mohammadreza kalantari]

Thanks.

i want to stem y[n]=y[n-2]+x[n]+2x[n-1] which is recursive and y[0]=1,y[-1]=5, x[n]=(1.5.^n).*u[n]

delta = @(d) d==0;

and also stem conv(y,delta)

can you help me?

[Star Strider]

This should be posted as a new Question.

[Mohammadreza kalantari]

I asked in that way too.

[Star Strider]

I will delete this Comment in a few minutes, then.

Answer 2

[Asif]

t=0:0.01:5; %Time from 0 to 5 seconds with a step size of 0.01 seconds

%Define the continous signal ( for example, a sinusoidal signal)

% Frequency=2; %Frequency of the sinusoid in HZ

Amplitude=1; % Amplitude of the sinusoid

Phase = pi/4; %phase of the sinusoid ( in radians)

signal = Amplitude*sin(2*pi*Frequency*t+Phase);

% plot the continuous signal

plot(t, signal,'b','Linewidth',6);

xlabel('xTime(s)X');

ylabel('Ampltitude');

title('Continuous Sinusoidal signal');

grid on