Re: Accuracy question
- To: mathgroup at smc.vnet.net
- Subject: [mg14105] Re: Accuracy question
- From: Robert Knapp <rknapp>
- Date: Fri, 25 Sep 1998 03:15:29 -0400
- Organization: Wolfram Research, Inc.
- References: <firstname.lastname@example.org>
- Sender: owner-wri-mathgroup at wolfram.com
Ersek, Ted R wrote:
> In the lines below SetPrecision[Round,False] makes it so Precision and
> accuracy return the actual floating point numbers that are used
> internally. $NumberMarks=True, makes it so (among other things)
> InputForm[num] returns all digits used internally, and the precision
> marks at the end of inexact numbers.
> Out shows exactly how Precision[x] is represented internally. Out
> shows that Precision[x] is the number closest to Log[10, 2^53].
> The next line shows exactly how Accuracy[x] is represented internally.
> Where does this number come from?
> Since accuracy is the number of digits to the right of the decimal I
> expect to get roughly 11.9. But why
> ( 11.8630751061039617` )?
The prinicpal you are looking for is
Precision[x] - Accuracy[x]
i.e. the difference between precision and accuracy is the scale (log
base 10 of the absolute value of the number)
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