Re: Re: derivative of a well-behaved function

*To*: mathgroup at smc.vnet.net*Subject*: [mg99728] Re: [mg99631] Re: derivative of a well-behaved function*From*: Syd Geraghty <sydgeraghty at me.com>*Date*: Tue, 12 May 2009 03:10:17 -0400 (EDT)*References*: <gtrl0i$1mf$1@smc.vnet.net> <200905100912.FAA09609@smc.vnet.net>

Hi Maxim, I get the following error message evaluating your expression with my system setup as listed below: > D[f[g[z]], z, Direction -> z0] == > g'[z]*D[f[w], w, Direction -> z0*g'[z]] /. w -> g[z] and Direction is highlighted in red. D::optx: Unknown option Direction in D[f[g[z]],z,Direction->z0]. >> D::optx: Unknown option Direction in D[f[w],w,Direction->z0 (g^\ [Prime])[z]]. >> D::optx: Unknown option Direction in D[f[g[z]],g[z],Direction->z0 (g^\ [Prime])[z]]. >> General::stop: Further output of D::optx will be suppressed during this calculation. >> In my documentation Direction is listed as an option for Limit[] Are you running a developer version? Syd Geraghty B.Sc, M.Sc. sydgeraghty at mac.com Mathematica 7.0.1 for Mac OS X x86 (64 - bit) (18th February 2009) MacOS X V 10.5.6 MacBook Pro 2.33 GHz Intel Core 2 Duo 2GB RAM On May 10, 2009, at 2:12 AM, m.r at inbox.ru wrote: > Essentially you want to compute a directional derivative of f[g[z]] > with g analytic and f non-analytic, where f == Abs and the direction > vector z0 == 1. Then (making up the notation as we go along) > > D[f[g[z]], z, Direction -> z0] == > g'[z]*D[f[w], w, Direction -> z0*g'[z]] /. w -> g[z]

**References**:**Re: derivative of a well-behaved function***From:*m.r@inbox.ru