Re: Table through zero...strange
- To: mathgroup at smc.vnet.net
- Subject: [mg67033] Re: Table through zero...strange
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Wed, 7 Jun 2006 05:10:19 -0400 (EDT)
- Organization: The Open University, Milton Keynes, UK
- References: <e63mqt$kqd$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
leptonic wrote: > Hello, > > When i type in Mathematica (version 4) Table[x, {x, -0.1, 0, 0.02}] > > it gives me {-0.1, -0.08, -0.06, -0.04, -0.02, -3.46945 x 10-18]} > but for example Table[x, {x, -0.1, 0, 0.05}] will give a reasonable > {-0.1, -0.05, 0.}. This is due to the arithmetic used for the computation: machine-precision in this case. The last entry is so close to zero that it can be deemed as equivalent to zero; use the built-in function Chop [1] to get the desired result {see In[1] and In[2]) or you may also use exact arithmetic by typing exact numbers as in inputs In[3] and In[4]. In[1]:= Table[Chop@x, {x, -0.1, 0, 0.02}] Out[1]= {-0.1, -0.08, -0.06, -0.04, -0.02, 0} In[2]:= Chop@Table[x, {x, -0.1, 0, 0.02}] Out[2]= {-0.1, -0.08, -0.06, -0.04, -0.02, 0} In[3]:= Table[x, {x, -1/10, 0, 2/100}] Out[3]= 1 2 3 1 1 {-(--), -(--), -(--), -(--), -(--), 0} 10 25 50 25 50 In[4]:= N@Table[x, {x, -1/10, 0, 2/100}] Out[4]= {-0.1, -0.08, -0.06, -0.04, -0.02, 0.} HTH, Jean-Marc [1]: http://documents.wolfram.com/mathematica/functions/Chop