Re: Unexpected behavior of Floor and IntegerPart
- To: mathgroup at smc.vnet.net
- Subject: [mg97962] Re: Unexpected behavior of Floor and IntegerPart
- From: dh <dh at metrohm.com>
- Date: Thu, 26 Mar 2009 05:25:25 -0500 (EST)
- References: <gqacr4$jbm$1@smc.vnet.net>
Hi Curtis,
look at:
Table[{i, i 100 - Round[100 i]}, {i, 0, 1, 0.01}]
and you will see that 0.29 (and 0.58 as well) is a little bit smaller
in the binary machine representation than in the decimal input
representation.
Daniel
Curtis Osterhoudt wrote:
> Dear List,
>
> I'm sure this is a result of non-infinite-precision arithmetic, but it would be nice to have a more consistent behavior:
>
> In[26]:= IntegerPart[0.29*100]
>
> Out[26]= 28
>
> In[25]:= Floor[0.29*100]
>
> Out[25]= 28
>
> In[27]:= Floor[(29/100)*100]
>
> Out[27]= 29
>
> In[32]:= (Floor[#1*100] & ) /@ Range[0, 1, 0.01]
>
> Out[32]= {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, \
> 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 28, 30, 31, 32, 33, \
> 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, \
> 51, 52, 53, 54, 55, 56, 57, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67,
> 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, \
> 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100}
>
> In[33]:= Differences[%]
>
> Out[33]= {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
> 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
> 1,
> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 1, 1, 1, 1, 1, 1, 1, \
> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
>
>
>
> An interesting hint as to what may be happening is obtained by:
>
> ListPlot[Differences[(Floor[#1*100] & ) /@ Range[0, 100, 0.01]]]
>
> Regards,
> C.O.
>
>
>