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Re: precision of a measurement (documentation related question)

• To: mathgroup at smc.vnet.net
• Subject: [mg61605] Re: precision of a measurement (documentation related question)
• From: Chris Chiasson <chris.chiasson at gmail.com>
• Date: Sun, 23 Oct 2005 05:46:16 -0400 (EDT)
• References: <acbec1a40510221346r2cee06c3led071a9eeb92d58b@mail.gmail.com> <acbec1a40510221456i64c176d7s73cd5110ac614ba1@mail.gmail.com>
• Sender: owner-wri-mathgroup at wolfram.com

To follow up, here is a function that people could use to compactly
enter in measurements and their (half) error range to obtain a number
in Mathematica that will have the appropriate significance attached to
it (no, I haven't really thought of handling complex numbers yet, but
I am sure someone smarter than myself could extend it).
Sig[x_,dx_]:=SetPrecision[x,-Log[10,Abs[dx/x]]]

Following my previous question:
Sig[30,0.5]
is the answer I was looking for earlier.

This Sig function could be combined with the Notation package to make
input even more tidy looking. One could also write a Notation to make
numbers with significance show error ranges by default...

Regards,

On 10/22/05, Chris Chiasson <chris.chiasson at gmail.com> wrote:
> Thanks to a Mention by Maxim in this thread:
> http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_frm/thread/1768e67ba5ac75f3?tvc=1&q=interval+significance
> and the documentation for Interval,
> I was able to figure out the answer to my question:
> FullForm@Interval[SetPrecision[x,-Log[10,dx/x]]]/.{{x\[Rule]30,
>       dx\[Rule]0.5},{x\[Rule]30,dx\[Rule]1}
>
> On 10/22/05, Chris Chiasson <chris.chiasson at gmail.com> wrote:
> > Hi Mathgroup,
> > If I know that a number (say in inches, measured on a ruler that only
> > has marks for inches) and its error are:
> > 30 + or - 0.5,
> > then looking at the help file for Precision, I see that the precision is:
> > -Log[10,dx/x]
> > In this case, is dx = 0.5 or is it equal to 1.0??
> > I have noticed that in either case, the number of significant
> > digits/the precision is less than 2.
> >
> > Your thoughts?
> > --
> > Chris Chiasson
> > http://chrischiasson.com/contact/chris_chiasson
> >
>
>
> --
> Chris Chiasson
> http://chrischiasson.com/contact/chris_chiasson
>


--
Chris Chiasson
http://chrischiasson.com/contact/chris_chiasson