Re: FractionalPart

*To*: mathgroup at smc.vnet.net*Subject*: [mg31255] Re: [mg31232] FractionalPart*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Tue, 23 Oct 2001 04:53:34 -0400 (EDT)*References*: <200110200827.EAA12211@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The situation you describe has to do with the way Mathematica handles numbers. Integers are exact, while reals are approximate. When you use Log[a], where a is a list of integers, the whole expression becomes real, and a very small error is introduced, in apparent contradiction to the obvious. In your example below, In[1]:= FractionalPart[x[[5]]] Out[1]= 1. because In[2]:= IntegerPart[x[[5]]] Out[2]= 4 The Help browser says "For exact numeric quantities, FractionalPart internally uses numerical approximations to establish its result. This process can be affected by the setting of the global variable $MaxExtraPrecision. " Tomas Garza Mexico City ----- Original Message ----- From: "Juan" <erfa11 at hotmail.com> To: mathgroup at smc.vnet.net Subject: [mg31255] [mg31232] FractionalPart > Hello. > I am new in Mathematica(also in english), and I have this question: > I would like to know the behavior of the function FractionalPart. > See here: > > In[1]:= a=Range[9]^2 > Out[1]= {1,4,9,16,25,36,49,64,81} > > In[2]:= x=Exp[.5 Log[a]] > Out[2]= {1,2.,3.,4.,5.,6.,7.,8.,9.} > > In[3]:= FractionalPart[x] > Out[3]= {0,0.,4.444089x10^-16,0.,0.,1.,0.,0.,1.,1.77639x10^-15} > > But it shoud be 0., all of them,no? > > Thanks. Juan > > > _________________________________________________________________ > Descargue GRATUITAMENTE MSN Explorer en http://explorer.msn.es/intl.asp > >

**References**:**FractionalPart***From:*"Juan" <erfa11@hotmail.com>