Re: Rounding Errors and Irregulars?
- To: mathgroup at smc.vnet.net
- Subject: [mg42046] Re: [mg42015] Rounding Errors and Irregulars?
- From: David Withoff <withoff at wolfram.com>
- Date: Tue, 17 Jun 2003 05:43:33 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
> Hi
>
> Is there a way to tell Mathematica not to *round* ?
>
> Example:
> In[x]:= SetPrecision[Pi, 10]
>
> Out[x]:= 3.14159265{4}
>
> The {4} is rounded, non-rounded should say {3}.
>
> Thanks,
> Jason
SetPrecision[Pi, 10] returns a number with a nominal
value of 3.141592653589793238458599 and a relative
uncertainty of 10^-10:
In[]:= InputForm[SetPrecision[Pi, 10]]
Out[]//InputForm= 3.141592653589793238458599`10
so SetPrecision did not do any rounding. Your example suggests
that perhaps what you want is different rounding (rounding down)
rather than no rounding. When the number is displayed Mathematica
will round it to the nearest 10-digit decimal. You can use
In[]:= SetPrecision[Floor[Pi 10^9]/10^9,10]
Out[]= 3.141592653
to get a number that is rounded down to the next smaller
10-digit decimal.