how to plot m(t)=cos(2*pi*9*t) 0<t<3 and m(t)=0 otherwise

how to plot m(t)=cos(2*pi*9*t) 0<t<3 and m(t)=0 otherwise

Answer 1

[Star Strider]

This works:

m = @(t) cos(2*pi*9*t) .* ((t > 0 ) & (t < 3));

t = linspace(-1, 4, 500);
Out = m(t);

figure(1)
plot(t, Out)
grid

[sameh mostafa]

i want better resolution

[Star Strider]

Change the ‘t’ assignment to:

t = linspace(-1, 4, 5000);

to improve the resolution by a factor of 10. Increase the third argument (here 5000) to get the resolution you want, if this is not enough.

Answer 2

[Ced]

You can use logical vectors to select certain parts of a vector.

t = -1:0.01:4;
m = zeros(length(t),1);
ind_interest = (t > 0 & t < 3); % this creates a logical vector
m(ind_interest) = cos(2*pi*9*t(ind_interest));

plot(t,m);
xlabel('time [s]')

Cheers

Answer 3

[sameh mostafa]

how to calculate the fourier transform and plot it of m(t)=cos(2*pi*9*t) 0<t<3 and m(t)=0 otherwise

Answer 4

[Juhi Maraskole]

X(t) = 1+ 1/2cos(2πt) + cos(4πt) + 2/3cos(6πt)