linear extrapolation to abscissa

[e-letter]

Readers,

I want to plot a least squares fit linear regression for the following data set:

x=0,5,10,15,20; y=16,45,77,101,125

Then I want to perform an extrapolation to obtain a value for x when
y=0. How do I perform this please?

The documentation is very unfriendly to a statistics and scilab
novice! First I tried to read about the interp function but didn't
understand the spline references so moved to interpln instead. ;)

The help section should have stated that plot2d is prerequisite
knowledge. So I read about plot2d. What does the function yi perform?
What is the purpose of the apostrophe (') in the example shown in the help?

Yours,

scilab at conference.jabber.org

scilab 411
mandriva 2008