Ciccarese,

Did you try solve? "The solve command solves one or more equations or inequalities for their unknowns."

acer and Robert,

Thanks A LOT for your time and effort.

Acer, I needed an analytical solution, and Robert's code solves the problem.

I didn't give enough background informaton I think: I am only interested in the positive quadrant (x and y are the price and quantity -and when you invert, quantity and price- of Economics). That piecewise function I gave is the monotone cubic spline fit to a given set of data, so it is necessarily one-to-one. So I knew the inverse existed but didn't know how to do it.

Now I just have to find a more automatic way of doing this because I need it for a simulation.

Best,

Ozgur Inal

Hey Mario,

Apparently, I couldn't express myself clearly:

I am trying to invert the piecewise function I wrote in 1-D math and you converted to 2-D math. I know what fsolve is for.

I used the built in procedure "solve" to invert the function, but when I compose the result and the original function I used in "solve", I don't get the identity.

Thank you casperyc but I don't quite understand; how will fsolve help me in this case?