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Groups > comp.lang.python > #70744
| From | Dennis Lee Bieber <wlfraed@ix.netcom.com> |
|---|---|
| Subject | Re: Significant digits in a float? |
| Date | 2014-04-29 20:33 -0400 |
| Organization | IISS Elusive Unicorn |
| References | <mailman.9549.1398700831.18130.python-list@python.org> <535f0f9f$0$29965$c3e8da3$5496439d@news.astraweb.com> <mailman.9565.1398741802.18130.python-list@python.org> <535f3bf7$0$11109$c3e8da3@news.astraweb.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.9594.1398818045.18130.python-list@python.org> (permalink) |
On 29 Apr 2014 05:43:19 GMT, Steven D'Aprano <steve@pearwood.info>
declaimed the following:
>does differ from value to value, I don't think he'll have much luck:
>given a float like 23.0, all we can say is that it has *at least* zero
>significant decimal places. 23.1 has at least one, 23.1111 has at least
>four.
>
I wouldn't even give it that... Since internally they (ignore binary
conversion) translate into
2.30E1, 2.31E1, and 2.31111E1
I'd claim 3-significant digits, 3-significant digits, and 6-significant
digits. (Heck, as I recall classical FORTRAN, they would be 0.230E2...)
>If you can put an upper bound on the precision, as Roy indicates he can,
>then perhaps a reasonable approach is to convert to a string rounded to
>four decimal places, then strip trailing zeroes:
>
That I'd agree with... once the data has been converted to binary
float, all knowledge of the source significant digits has been lost.
Then confuse matters with the facet that in a math class
1.1 * 2.2 => 2.42
but in a physics or chemistry class the recommended result is
1.1 * 2.2 => 2.4
(one reason slide-rules were acceptable for so long -- and even my high
school trig course only required slide-rule significance even though half
the class had scientific calculators [costing >$100, when a Sterling
slide-rule could still be had for <$10]) <G>
--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/
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Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-28 12:00 -0400
Re: Significant digits in a float? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-29 02:34 +0000
Re: Significant digits in a float? Ben Finney <ben@benfinney.id.au> - 2014-04-29 13:23 +1000
Re: Significant digits in a float? Steven D'Aprano <steve@pearwood.info> - 2014-04-29 05:43 +0000
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-29 20:33 -0400
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 20:42 -0400
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-30 20:02 -0400
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-04-30 22:54 -0500
Re: Significant digits in a float? Paul Rubin <no.email@nospam.invalid> - 2014-04-30 20:56 -0700
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-04-30 23:16 -0500
Re: Significant digits in a float? William Ray Wing <wrw@mac.com> - 2014-05-01 11:53 -0400
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-05-06 11:29 -0500
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-01 22:06 -0400
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-05-06 09:51 -0500
Re: Significant digits in a float? alister <alister.nospam.ware@ntlworld.com> - 2014-05-06 15:18 +0000
Re: Significant digits in a float? Joel Goldstick <joel.goldstick@gmail.com> - 2014-05-06 12:14 -0400
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-06 19:48 -0400
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-05-01 08:56 -0400
Re: Significant digits in a float? Larry Hudson <orgnut@yahoo.com> - 2014-05-01 12:51 -0700
Re: Significant digits in a float? Adam Funk <a24061@ducksburg.com> - 2014-05-01 22:05 +0100
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-01 21:47 -0400
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-05-06 09:59 -0500
[OT] Silde rules [was Re: Significant digits in a float?] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-06 16:10 +0000
Re: [OT] Silde rules Ben Finney <ben@benfinney.id.au> - 2014-05-07 10:01 +1000
Re: Significant digits in a float? Adam Funk <a24061@ducksburg.com> - 2014-05-01 21:55 +0100
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-01 22:26 -0400
Re: Significant digits in a float? Adam Funk <a24061@ducksburg.com> - 2014-05-08 20:58 +0100
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 09:38 -0400
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 02:30 +1000
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 19:53 -0400
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 10:13 +1000
Re: Significant digits in a float? Ben Finney <ben@benfinney.id.au> - 2014-04-30 10:13 +1000
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 10:17 +1000
Re: Significant digits in a float? Ben Finney <ben@benfinney.id.au> - 2014-04-30 10:20 +1000
Re: Significant digits in a float? Grant Edwards <invalid@invalid.invalid> - 2014-04-30 18:19 +0000
Re: Significant digits in a float? Ned Batchelder <ned@nedbatchelder.com> - 2014-04-29 12:47 -0400
Re: Significant digits in a float? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-30 09:45 +1200
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 02:59 +1000
Re: Significant digits in a float? Adam Funk <a24061@ducksburg.com> - 2014-04-29 21:16 +0100
Re: Significant digits in a float? Mark H Harris <harrismh777@gmail.com> - 2014-04-29 15:39 -0500
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 07:15 +1000
Re: Significant digits in a float? Ryan Hiebert <ryan@ryanhiebert.com> - 2014-04-29 15:42 -0500
Re: Significant digits in a float? emile <emile@fenx.com> - 2014-04-29 15:42 -0700
Re: Significant digits in a float? alister <alister.nospam.ware@ntlworld.com> - 2014-04-30 09:03 +0000
Re: Significant digits in a float? Grant Edwards <invalid@invalid.invalid> - 2014-04-30 18:21 +0000
Re: Significant digits in a float? emile <emile@fenx.com> - 2014-05-01 09:34 -0700
Re: Significant digits in a float? alister <alister.nospam.ware@ntlworld.com> - 2014-05-01 17:13 +0000
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 08:51 +1000
Re: Significant digits in a float? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-30 20:14 +1200
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 18:27 +1000
Re: Significant digits in a float? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-30 14:05 +0100
Re: Significant digits in a float? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-30 00:34 +0100
Re: Significant digits in a float? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-29 20:37 -0400
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 20:45 -0400
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 10:45 +1000
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 20:48 -0400
Re: Significant digits in a float? Ethan Furman <ethan@stoneleaf.us> - 2014-04-29 19:31 -0700
Re: Significant digits in a float? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-30 02:59 +0000
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-29 23:30 -0400
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 13:40 +1000
Re: Significant digits in a float? Chris Angelico <rosuav@gmail.com> - 2014-04-30 13:03 +1000
Re: Significant digits in a float? Roy Smith <roy@panix.com> - 2014-04-30 08:01 -0400
Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Ethan Furman <ethan@stoneleaf.us> - 2014-04-30 06:14 -0700
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Ethan Furman <ethan@stoneleaf.us> - 2014-04-30 07:02 -0700
Re: Off-topic circumnavigating the earth in a mile or less Adam Funk <a24061@ducksburg.com> - 2014-05-01 21:52 +0100
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Chris Angelico <rosuav@gmail.com> - 2014-05-01 00:27 +1000
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Chris Angelico <rosuav@gmail.com> - 2014-05-01 05:10 +1000
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Ryan Hiebert <ryan@ryanhiebert.com> - 2014-04-30 10:24 -0500
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-30 17:46 -0600
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Terry Reedy <tjreedy@udel.edu> - 2014-04-30 22:20 -0400
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-05-01 18:16 +1200
Re: Off-topic circumnavigating the earth in a mile or less Adam Funk <a24061@ducksburg.com> - 2014-05-01 21:57 +0100
Re: Off-topic circumnavigating the earth in a mile or less Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-05-01 22:49 +0100
Re: Off-topic circumnavigating the earth in a mile or less alister <alister.nospam.ware@ntlworld.com> - 2014-05-02 08:49 +0000
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Chris Angelico <rosuav@gmail.com> - 2014-05-01 11:57 +1000
Re: Off-topic circumnavigating the earth in a mile or less [was Re: Significant digits in a float?] Vlastimil Brom <vlastimil.brom@gmail.com> - 2014-05-01 09:49 +0200
Re: Significant digits in a float? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-30 02:50 +0000
Re: Significant digits in a float? Grant Edwards <invalid@invalid.invalid> - 2014-04-30 18:18 +0000
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