Reply by June 4, 20072007-06-04
```Hello, I'm trying to work my way through a few introductory courses
that I taped two years ago. I've been listening to them during the
weekends and have to get straight on things! I've struggled through
the material many years ago and am keeping my fingers crossed.

Basically, I'm hoping for a tuturial from you directed to my specific
questions below.

If the input to the below functions is one or two series of integer
numbers. What is an intuitive explanation for plots involving the
auto-correlation function and cross-correlation function. What type of
plot shapes are possible? What do these plots mean at different points
in the plot?

Can you give me some complete practical examples on how to use these
plots which give the input data values, plots, and what the plots mean
in general and at specific points in the plots?

My courses seem to all plot sinc-like graphs.

The way I have been trying to explain the above process to myself is
to realize that a function takes two numbers as input and produces one
output value, that's it.

Thank you,
Christopher Lusardi

P.S.: I own all of Papoulis' books etc etc.

```