Inverse of a six-parameter asymmetric sigmoidal curve

*To*: mathgroup at smc.vnet.net*Subject*: [mg111178] Inverse of a six-parameter asymmetric sigmoidal curve*From*: spiceman <aspiess at uke.de>*Date*: Fri, 23 Jul 2010 07:08:48 -0400 (EDT)

Hi everybody, does anybody have a clue how to get Mathematica to deliver the inverse of the following function? fct := c + (k * Log[x]) + (d - c)/(1 + Exp[b*(Log[x] - Log[e])])^f Solve[fct == y, x] Solve::tdep: The equations appear to involve the variables to be solved for in an essentially non-algebraic way. I suppose I have to transform somehow. Any clues? Omitting k*Log[x] works... Thnaks in advance, -ans