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Groups > comp.lang.python > #111235 > unrolled thread
| Started by | Lawrence D’Oliveiro <lawrencedo99@gmail.com> |
|---|---|
| First post | 2016-07-09 22:54 -0700 |
| Last post | 2016-07-12 00:17 -0400 |
| Articles | 4 on this page of 84 — 19 participants |
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Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-09 22:54 -0700
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-10 01:21 -0600
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-10 17:34 -0700
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-11 09:04 -0600
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve@pearwood.info> - 2016-07-12 02:28 +1000
Re: Curious Omission In New-Style Formats Ethan Furman <ethan@stoneleaf.us> - 2016-07-11 10:24 -0700
Re: Curious Omission In New-Style Formats Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-07-12 11:47 +1200
Re: Curious Omission In New-Style Formats Ethan Furman <ethan@stoneleaf.us> - 2016-07-11 17:24 -0700
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-11 19:16 -0600
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-11 12:38 -0600
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve@pearwood.info> - 2016-07-12 13:38 +1000
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-13 00:21 -0600
Re: Curious Omission In New-Style Formats Marko Rauhamaa <marko@pacujo.net> - 2016-07-13 09:57 +0300
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-13 00:05 -0700
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-07-13 18:49 +1000
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-13 16:01 +0200
Re: Curious Omission In New-Style Formats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-07-13 20:04 -0400
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-13 15:24 -0700
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-13 18:45 -0600
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-13 20:39 -0700
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-13 23:18 -0600
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-07-14 17:47 +1000
Re: Curious Omission In New-Style Formats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-07-14 07:34 -0400
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-14 08:30 -0600
Re: Curious Omission In New-Style Formats Marko Rauhamaa <marko@pacujo.net> - 2016-07-14 19:02 +0300
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-14 11:10 -0600
Re: Curious Omission In New-Style Formats Marko Rauhamaa <marko@pacujo.net> - 2016-07-14 20:30 +0300
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-14 18:17 -0600
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-14 18:08 -0700
Re: Curious Omission In New-Style Formats Marko Rauhamaa <marko@pacujo.net> - 2016-07-15 09:06 +0300
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 09:54 +0200
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-15 11:40 +0300
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve@pearwood.info> - 2016-07-15 20:56 +1000
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 13:44 +0200
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-15 16:38 +0300
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 16:47 +0200
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-15 16:13 +0300
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve@pearwood.info> - 2016-07-16 01:12 +1000
Re: Curious Omission In New-Style Formats Random832 <random832@fastmail.com> - 2016-07-15 09:39 -0400
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 16:32 +0200
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 13:05 +0200
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-15 16:28 +0300
Re: Curious Omission In New-Style Formats Steven D'Aprano <steve@pearwood.info> - 2016-07-16 01:13 +1000
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-15 18:27 +0300
Re: Curious Omission In New-Style Formats Marko Rauhamaa <marko@pacujo.net> - 2016-07-15 12:20 +0300
Re: Curious Omission In New-Style Formats Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-15 12:44 +0200
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-14 16:26 -0700
Re: Curious Omission In New-Style Formats Robert Kern <robert.kern@gmail.com> - 2016-07-14 16:17 +0100
Re: Curious Omission In New-Style Formats Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-15 16:35 -0700
Re: Curious Omission In New-Style Formats Chris Angelico <rosuav@gmail.com> - 2016-07-16 10:57 +1000
Re: Curious Omission In New-Style Formats MRAB <python@mrabarnett.plus.com> - 2016-07-14 01:59 +0100
Re: Curious Omission In New-Style Formats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-07-13 07:46 -0400
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-13 16:04 +0300
Re: Curious Omission In New-Style Formats Chris Angelico <rosuav@gmail.com> - 2016-07-13 23:00 +1000
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-13 16:16 +0300
Re: Curious Omission In New-Style Formats Chris Angelico <rosuav@gmail.com> - 2016-07-13 23:49 +1000
Re: Curious Omission In New-Style Formats Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-07-13 17:23 +0300
Re: Curious Omission In New-Style Formats Chris Angelico <rosuav@gmail.com> - 2016-07-14 00:28 +1000
Re: Curious Omission In New-Style Formats Terry Reedy <tjreedy@udel.edu> - 2016-07-11 14:54 -0400
Re: Curious Omission In New-Style Formats Ian Kelly <ian.g.kelly@gmail.com> - 2016-07-11 13:27 -0600
Re: Curious Omission In New-Style Formats Michael Torrie <torriem@gmail.com> - 2016-07-11 14:06 -0600
Re: Curious Omission In New-Style Formats Random832 <random832@fastmail.com> - 2016-07-11 16:34 -0400
Re: Curious Omission In New-Style Formats Terry Reedy <tjreedy@udel.edu> - 2016-07-11 16:52 -0400
What is precision of a number representation? (was: Curious Omission In New-Style Formats) Ben Finney <ben+python@benfinney.id.au> - 2016-07-12 06:56 +1000
Re: What is precision of a number representation? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-07-11 23:28 +0100
Re: What is precision of a number representation? Ethan Furman <ethan@stoneleaf.us> - 2016-07-11 14:22 -0700
Re: What is precision of a number representation? (was: Curious Omission In New-Style Formats) Chris Angelico <rosuav@gmail.com> - 2016-07-12 07:51 +1000
Re: What is precision of a number representation? (was: Curious Omission In New-Style Formats) Jan Coombs <jenfhaomndgfwutc@murmic.plus.com> - 2016-07-12 00:14 +0100
Re: What is precision of a number representation? (was: Curious Omission In New-Style Formats) Chris Angelico <rosuav@gmail.com> - 2016-07-12 09:57 +1000
Re: What is precision of a number representation? (was: Curious Omission In New-Style Formats) Steven D'Aprano <steve@pearwood.info> - 2016-07-12 14:19 +1000
Re: What is precision of a number representation? (was: Curious Omission In New-Style Formats) Chris Angelico <rosuav@gmail.com> - 2016-07-12 14:36 +1000
Re: What is precision of a number representation? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-12 11:50 +0200
Re: What is precision of a number representation? Marko Rauhamaa <marko@pacujo.net> - 2016-07-12 13:27 +0300
Re: What is precision of a number representation? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-07-12 13:02 +0200
Re: What is precision of a number representation? Steven D'Aprano <steve@pearwood.info> - 2016-07-12 23:16 +1000
Re: What is precision of a number representation? Ethan Furman <ethan@stoneleaf.us> - 2016-07-11 15:17 -0700
Re: What is precision of a number representation? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-07-12 16:21 +1000
Re: What is precision of a number representation? Random832 <random832@fastmail.com> - 2016-07-12 09:36 -0400
Re: What is precision of a number representation? Ethan Furman <ethan@stoneleaf.us> - 2016-07-11 15:29 -0700
Re: Curious Omission In New-Style Formats Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-07-12 11:26 +1200
Re: What is precision of a number representation? Chris Angelico <rosuav@gmail.com> - 2016-07-12 11:57 +1000
Re: What is precision of a number representation? Ben Finney <ben+python@benfinney.id.au> - 2016-07-12 13:41 +1000
Re: What is precision of a number representation? Terry Reedy <tjreedy@udel.edu> - 2016-07-12 00:14 -0400
Re: What is precision of a number representation? Terry Reedy <tjreedy@udel.edu> - 2016-07-12 00:17 -0400
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| From | Chris Angelico <rosuav@gmail.com> |
|---|---|
| Date | 2016-07-12 11:57 +1000 |
| Subject | Re: What is precision of a number representation? |
| Message-ID | <mailman.3.1468288640.21009.python-list@python.org> |
| In reply to | #111273 |
On Tue, Jul 12, 2016 at 8:17 AM, Ethan Furman <ethan@stoneleaf.us> wrote: >> This is why it's important to be able to record precisions of >> arbitrary numbers. If I then measure the width of this corridor with a >> laser, I could get an extremely precise answer - say, 2,147 >> millimeters, with a precision of four significant digits, and >> excellent accuracy. But if I multiply those numbers together to >> establish the floor area of the corridor, the result does NOT have >> four significant figures. It would be 64 square meters (not 64.41), >> and the accuracy would be pretty low (effectively, the *in*accuracies >> of both measurements get combined). But on the other hand, if you want >> to know whether your new fridge will fit, you could measure it with >> the same laser and come up with a figure of 1,973 mm (four sig fig), >> which would mean your clearance is 174mm (four sig fig). How do you >> record this? Is it 174.0? 0174? "174 with four significant figures"? > > > 174.0, because those last tenths of a millimeter could be very important, > while knowledge that there are no thousands of millimeters is already > present. > But I never measured it to tenths of a millimeter. The display on my laser measurer (I don't actually have one, by the way, so all this is complete fabrication for the sake of the example) displays integer millimeters, with an implicit "+/- 0.5 mm". ChrisA
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| From | Ben Finney <ben+python@benfinney.id.au> |
|---|---|
| Date | 2016-07-12 13:41 +1000 |
| Subject | Re: What is precision of a number representation? |
| Message-ID | <mailman.4.1468294936.21009.python-list@python.org> |
| In reply to | #111273 |
Ethan Furman <ethan@stoneleaf.us> writes: > On 07/11/2016 01:56 PM, Ben Finney wrote: > > > Precision is not a property of the number. It is a property of the > > *representation* of that number. > > > > The representation “1×10²” has a precision of one digit. > > The representation “100” has a precision of three digits. > > The representation “00100” has a precision of five digits. > > The representation “100.00” also has a precision of five digits. > > […] you haven't explained how 00100 is more precise than 100. I haven't made any claim about “more precise” in the above. But if you want such claims, here are comparable representations in increasing order of precision: * “0 ×10²” has one digit of precision. * “0.0 ×10²” has two digits of precison. * “0.01 ×10²” has three digits of precision. * “0.010 ×10²” has four digits of precision. * “0.0100 ×10²” has five digits of precision. * “0.01000 ×10²” has six digits of precision. Again, these might all be representations of the same number or of different numbers; the representation claims only to represent a number within a range of tolerance. In decimal notation, some of the above can't be written with the same precision. I could invent a representation — e.g. show “?” as a place-holder for a digit not within the precision level. In that system, the equivalent representations would be: * “0????” * “00???” * “001??” * “0010?” * “00100” * “00100.0” Each of these claims to represent a quantity beginning at the ten-thousands place, with increasing levels of precision in the claim. So the comparison that invites is to show where the range of tolerance for the representation ends. The fewer digits of precision, the less precise the representation claims to be. -- \ “I find the whole business of religion profoundly interesting. | `\ But it does mystify me that otherwise intelligent people take | _o__) it seriously.” —Douglas Adams | Ben Finney
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| From | Terry Reedy <tjreedy@udel.edu> |
|---|---|
| Date | 2016-07-12 00:14 -0400 |
| Subject | Re: What is precision of a number representation? |
| Message-ID | <mailman.5.1468296898.21009.python-list@python.org> |
| In reply to | #111273 |
On 7/11/2016 5:51 PM, Chris Angelico wrote: > This is why it's important to be able to record precisions of > arbitrary numbers. If I then measure the width of this corridor with a > laser, I could get an extremely precise answer - say, 2,147 > millimeters, with a precision of four significant digits, and > excellent accuracy. But if I multiply those numbers together to > establish the floor area of the corridor, the result does NOT have > four significant figures. It would be 64 square meters (not 64.41), > and the accuracy would be pretty low (effectively, the *in*accuracies > of both measurements get combined). But on the other hand, if you want > to know whether your new fridge will fit, you could measure it with > the same laser and come up with a figure of 1,973 mm (four sig fig), > which would mean your clearance is 174mm (four sig fig). Wrong as to the last point. 2147 - 1973 = 174 has only 3 sig. figures. 2147 - 2144 = 3 has 1 significant figure. Subtraction of nearly equal numbers can cancel sig. figures. > How do you > record this? Is it 174.0? 0174? "174 with four significant figures"? None of these. -- Terry Jan Reedy
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| From | Terry Reedy <tjreedy@udel.edu> |
|---|---|
| Date | 2016-07-12 00:17 -0400 |
| Subject | Re: What is precision of a number representation? |
| Message-ID | <mailman.6.1468297205.21009.python-list@python.org> |
| In reply to | #111273 |
On 7/11/2016 6:17 PM, Ethan Furman wrote: > On 07/11/2016 02:51 PM, Chris Angelico wrote: >> This is why it's important to be able to record precisions of >> arbitrary numbers. If I then measure the width of this corridor with a >> laser, I could get an extremely precise answer - say, 2,147 >> millimeters, with a precision of four significant digits, and >> excellent accuracy. But if I multiply those numbers together to >> establish the floor area of the corridor, the result does NOT have >> four significant figures. It would be 64 square meters (not 64.41), >> and the accuracy would be pretty low (effectively, the *in*accuracies >> of both measurements get combined). But on the other hand, if you want >> to know whether your new fridge will fit, you could measure it with >> the same laser and come up with a figure of 1,973 mm (four sig fig), >> which would mean your clearance is 174mm (four sig fig). How do you >> record this? Is it 174.0? 0174? "174 with four significant figures"? > > 174.0, A common fallacy. There are only 3 significant figures because one, the first, was cancelled by subtracting close numbers. The same is true of adding numbers of opposite signs. -- Terry Jan Reedy
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