Originally Posted by

**jnscollier** ...

A: I am trying to derive a mathematical function for an inverse signoid line that starts out at the max value and over time declines to a min value that I define.

...

I basically want the formula to start out at the Max CPC (Let's say $10) and as cost increases, to decrease logarithmically but not below a MIN CPC value (Let's say $0.50). At the MIN CPC value, I want it to be a horizontal asymptote.

Is there a function that will let me input the Max CPC and MIN CPC to be the Ceiling and Floor and then essentially decay based on the level of Total Cost?