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Re: Best syntax for derivative

• To: mathgroup at smc.vnet.net
• Subject: [mg96418] Re: [mg96386] Best syntax for derivative
• From: Carl Woll <carlw at wolfram.com>
• Date: Fri, 13 Feb 2009 03:43:01 -0500 (EST)
• References: <200902121141.GAA08658@smc.vnet.net> <49943ED6.6070407@wolfram.com> <38178b720902120742v622b315es505bb5bd96b52c59@mail.gmail.com>

Aaron Fude wrote:

> Thanks. That's cool. May I ask a follow up question?
>  
> What if I want to have  g=f^2?
>  
> Is there a similar alternative to
>  
> g[x_, y_, z_] := f[x, y, z]^2?
>  
> Thanks again!

The Derivative thing can work because the number of arguments it gets 
determines how many arguments f has. In your example this information is 
unavailable, so you'll need to use Slot objects to achieve the same effect:

g = f[##]^2&

Carl

>  
>
>
>  
> On Thu, Feb 12, 2009 at 10:23 AM, Carl Woll <carlw at wolfram.com 
> <mailto:carlw at wolfram.com>> wrote:
>
>     Aaron Fude wrote:
>
>         Hi,
>
>         Suppose I have a function of three variables
>
>         f[x_, y_, z_]:=Sin[x y z]
>
>         And I want to construct g[x, y, z] which is the partial
>         derivative of f
>         [] with respect to y. I do
>
>         f[x_, y_, z_] := Sin[x y z]
>         g[x_, y_, z_] := D[f[x, temp, z], temp] /. temp -> y
>
>         but I'm sure there is something better. Something along the
>         lines of
>
>         g = Partial[f, 2]
>
>         Many thanks in advance.
>
>         Aaron
>
>          
>
>     It's:
>
>     g = Derivative[0, 1, 0][f]
>
>     Carl Woll
>     Wolfram Research
>
>

• References:
  • Best syntax for derivative
    • From: Aaron Fude <aaronfude@gmail.com>