Re: How to evaluate the Laplacian of a function as a function?

*To*: mathgroup at smc.vnet.net*Subject*: [mg114381] Re: How to evaluate the Laplacian of a function as a function?*From*: Roland Franzius <roland.franzius at uos.de>*Date*: Thu, 2 Dec 2010 05:42:45 -0500 (EST)*References*: <id4sma$ci5$1@smc.vnet.net>

Am 01.12.2010 08:15, schrieb Iliyan Georgiev: > Hi, > > I have a stupid problem and cannot find a solution anywhere. I have > the function > > func[x_,y_] := 3/Pi*(1 - x^2 + y^2))^2 > > which I need the Laplacian of: > > funcLapl := Laplacian[func[Xx,Yy]] > > The Laplacian is computed correctly, but how can I treat the result as > a function? I want to be able to evaluate/plot the Laplacian. I tried > many things and I'm frustrated. My current solution is to manually > copy the derived Laplacian and create a function from that. It's > obviously not a good solution. For expressions, map second derivatives of expression into varaibel list, convert the list to a sum and the pair of variable list and body into a Function LaplaceOperator[expr_, x_List]:= ff[ x, Plus@@ (D[expr,#,#]&/@x))] /. ff->Function Another way to force evaluation inside a function body during body preprocessing is using Evaluate LaplaceOperator[expr_, x_List] := Function[x, Evaluate[Plus @@ (D[expr, #, #] & /@ x)]] -- Roland Franzius