Re: Automatic expansion of Log[a^n] for a, n explicit positive integers?

*To*: mathgroup at smc.vnet.net*Subject*: [mg28265] Re: [mg28180] Automatic expansion of Log[a^n] for a, n explicit positive integers?*From*: BobHanlon at aol.com*Date*: Fri, 6 Apr 2001 01:53:15 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Here are two alternatives depending on how you want the function to behave for other cases. loga[b_:E, x_Integer?Positive] := Plus @@ (#[[2]]*Log[b, #[[1]]]& /@ FactorInteger[x]); loga[b_:E, x_] := Log[b, x]; logb[b_:E, x_Integer?Positive] := Module[{fi = FactorInteger[x]}, If[Length[fi] == 1, fi[[1,2]]*Log[b, fi[[1,1]]], Log[b, x]]]; logb[b_:E, x_] := Log[b, x]; Table[{k, loga[k], logb[k]}, {k, 10}] // TableForm Bob Hanlon In a message dated 2001/4/3 2:46:08 AM, anlauf at hep.tu-darmstadt.de writes: >is there a way to force Mathematica 4.0 to always expand expressions like > >Log[4], Log[8], Log[16], etc. to 2*Log[2] etc. > >automatically? > >It is very annoying to have such logarithms expanded manually each >time they pop up again... > >PowerExpand[] apparently does not help/work. >