Re: what tool for extrapolation beyond input range?

[Andrew Schulman <andrex@alumni.utexas.net>]

> What Debian tool can I use to answer
>    If I sold
>    4 burgers at 4:00
>    5 burgers at 5:00
>    6 burgers at 6:00
>    how many burgers might I be expected to sell at 7:00?
> plotutils: no. gmt: no. gnuplot: no(?)  All of them dare not to
> extrapolate beyond the input edges.

First, realize that the answer to your question is arbitrary, or 
unknown.  You have no idea how many burgers you're going to sell at 7 
o'clock.  Maybe a movie will let out at 6:45, so you'll sell 50.  Or 
maybe a hail storm will come up, sending everyone home and you'll sell 
zero.

You can write down a model, e.g. linear growth of sales over time (which 
is apparently what you want to do here), but it has no empirical 
validity.  It is just an assumption.  In fact you can trivially get any 
answer at all, by writing down a different model assumption.

That said, it seems that you want software that will allow you to

(1) specify a model (e.g. linear trend of sales over time) and estimate 
its parameters to give the best fit to the above-mentioned data, and

(2) plot the results.

For that I suggest octave or R.