I'm having a really hard time to find the inverse of the following six-parameter sigmoidal function:
y = c + k*log(x) + (d-c)/(1+exp(b*(log(x)-log(e))))^f
k, c, d, e and f are parameters.
I need to solve the function to x.
Any hints on what transformations are necessary?
If I omit k*log(x) it's easy, but this term makes it hard somehow...
Thanks in advance,