How to plot digital sequence in MATLAB

I have to plot following digital sequence in MATLAB: a^n * u[n]. a is just a constant. How do I do this?

Thanks

Answer 1

[David Hill]

n=1:length(u);
a=1.7;
plot(n,a.^n.*u);%assuming u is a vector

[Tommy P]

Is it possible to show this as a discrete spectrum? instead of a line, more someting like this as lay-out?

[Allen]

You can also plot this using a bar plot vs. a line plot.

bar(n,a.^n.*u)

[Walter Roberson]

stem()

Note: u[n] is not a vector as such: it indicates the unit step function.

Answer 2

[Walter Roberson]

If you are certain that all of your values are finite, then you can replace u[n] by (n>=0)

If you have negative infinite values then it is not obvious that multiplying by the unit step function is well defined.