Re: simple problem with Map?!?

*To*: mathgroup at smc.vnet.net*Subject*: [mg49563] Re: [mg49480] simple problem with Map?!?*From*: DrBob <drbob at bigfoot.com>*Date*: Fri, 23 Jul 2004 06:00:28 -0400 (EDT)*References*: <200407211040.GAA07884@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

Study the results of this code: d0 = {30, 60}; pppp = N[#/(Plus @@ #)] & /@ d0 // Trace (snip) The pure function N[#/(Plus @@ #)] & is applied to each element of d0 (30 and 60) separately. Plus@@30 is 30, so we get N[30/30], which is N[1], and that's 1. That's what happens for every element of d0, so the result is {1.,1.}. Probably what you want is just: N[d0/Tr@d0] {0.333333,0.666667} Bobby On Wed, 21 Jul 2004 06:40:32 -0400 (EDT), Relishguy <relishguy at pluggedin.org> wrote: > I do not understand why the last evaluation ends up screwed: > > In[1]:= d0 = {30,60,180,60,30}; > > In[2]:= tt = Plus @@ d0 > Out[2]= 360 > > In[3]:= pp = N[d0 / tt] > Out[3]= {0.0833333,0.166667,0.5,0.166667,0.0833333} > > In[4]:= ppp = N[d0 / (Plus @@ d0)] > Out[4]= {0.0833333,0.166667,0.5,0.166667,0.0833333} > > In[5]:= pppp = N[# / (Plus @@ #)]& /@ d0 > Out[5]= {1.,1.,1.,1.,1.} > > Can anyone explain this simply? Do I need Hold[] or Evaluate[] somewhere? > > TIA. > > Regards.. > > > -- DrBob at bigfoot.com www.eclecticdreams.net

**References**:**simple problem with Map?!?***From:*relishguy@pluggedin.org (Relishguy)