How to plot signal with unit step?

I want to plot the following signal in matlab but I am not sure how to do this with the unit step response involved.

    x[n] = ((4/5)^n)u[n]
    -5 < n < 20

Answer 1

[Hamoon]

You can use heaviside function:

 n = -5:1:20;
 x = ((4/5).^n).*heaviside(n);
 stem(n,x)

Bet be aware heaviside(0)=0.5

[Bilal Siddiqui]

excellent. Thank You. I was missing '.' before * so was getting an error.

[Hamoon]

you can also use this if you want to have u[0]=0:

 n = -5:1:20;
 myStep = @(n) (n>0);
 x = ((4/5).^n).*myStep(n);
 stem(n,x)

[Hamoon]

My Pleasure...

Answer 2

[Kamalika Saha]

n = -5:1:20;

x = ((4/5).^n).*heaviside(n);

stem(n,x)