Solver. When a model is liner and when it's not?

[Guest]

If I use a function like MAX in my xls model, does that makes my model non
linear?
My solver (xls 2000) is not working with non linear models...

Tx,
PV

 

[Bill Martin]

It's even worse than non-linear. A simple non-linear system might be Y=X*X.

What you are describing is a discontinuous function - one with breakpoints where
the equation changes. In my experience Solver can deal with simple non-linear
systems, but is totally unable to deal with discontinuous functions.

My approach for discontinuous systems is to solve them "manually". If I have
some system Y=f(X) then I will create a table of X values I want evaluated and
write a macro to repeatedly plug those X values into the spreadsheet and pull
back the resultant Y into that table. Then you can easily plot the table and
see what you've got. I find the need to do this because heavily discontinuous
systems (1000 If/then statements say) may result in very narrow spikes in the
response function that may be significant, or may not. You've got to examine
them by eye to decide.

More than you wanted to know. Good luck...

Bill