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Significant digits in a float?

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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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#70682 — Significant digits in a float?

I'm using Python 2.7

I have a bunch of floating point values.  For example, here's a few (printed as reprs):

38.0
41.2586
40.75280000000001
49.25
33.795199999999994
36.837199999999996
34.1489
45.5

Fundamentally, these numbers have between 0 and 4 decimal digits of precision, and I want to be able to intuit how many each has, ignoring the obvious floating point roundoff problems.  Thus, I want to map:

38.0  ==> 0
41.2586 ==> 4
40.75280000000001 ==> 4
49.25 ==> 2
33.795199999999994 ==> 4
36.837199999999996 ==> 4
34.1489 ==> 4
45.5 ==> 1

Is there any clean way to do that?  The best I've come up with so far is to str() them and parse the remaining string to see how many digits it put after the decimal point.

The numbers are given to me as Python floats; I have no control over that.  I'm willing to accept that fact that I won't be able to differentiate between float("38.0") and float("38.0000").  Both of those map to 1, which is OK for my purposes.

---
Roy Smith
roy@panix.com

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#70702

On Mon, 28 Apr 2014 12:00:23 -0400, Roy Smith wrote:

[...]
> Fundamentally, these numbers have between 0 and 4 decimal digits of
> precision, 

I'm surprised that you have a source of data with variable precision, 
especially one that varies by a factor of TEN THOUSAND. The difference 
between 0 and 4 decimal digits is equivalent to measuring some lengths to 
the nearest metre, some to the nearest centimetre, and some to the 
nearest 0.1 of a millimetre. That's very unusual and I don't know what 
justification you have for combining such a mix of data sources.

One possible interpretation of your post is that you have a source of 
floats, where all the numbers are actually measured to the same 
precision, and you've simply misinterpreted the fact that some of them 
look like they have less precision. Since you indicate that 4 decimal 
digits is the maximum, I'm going with 4 decimal digits. So if your data 
includes the float 23.5, that's 23.5 measured to a precision of four 
decimal places (that is, it's 23.5000, not 23.5001 or 23.4999).

On the other hand, if you're getting your values as *strings*, that's 
another story. If you can trust the strings, they'll tell you how many 
decimal places: "23.5" is only one decimal place, "23.5000" is four.

But then what to make of your later example?

> 40.75280000000001 ==> 4

Python floats (C doubles) are quite capable of distinguishing between 
40.7528 and 40.75280000000001. They are distinct numbers:

py> 40.75280000000001 - 40.7528
7.105427357601002e-15

so if a number is recorded as 40.75280000000001 presumably it is because 
it was measured as 40.75280000000001. (How that precision can be 
justified, I don't know! Does it come from the Large Hadron Collider?) If 
it were intended to be 40.7528, I expect it would have be recorded as 
40.7528. What reason do you have to think that something recorded to 14 
decimal places was only intended to have been recorded to 4?

Without knowing more about how your data is generated, I can't advise you 
much, but the whole scenario as you have described it makes me think that 
*somebody* is doing something wrong. Perhaps you need to explain why 
you're doing this, as it seems numerically broken.


> Is there any clean way to do that?  The best I've come up with so far is
> to str() them and parse the remaining string to see how many digits it
> put after the decimal point.

I really think you need to go back to the source. Trying to infer the 
precision of the measurements from the accident of the string formatting 
seems pretty dubious to me.

But I suppose if you wanted to infer the number of digits after the 
decimal place, excluding trailing zeroes (why, I do not understand), up 
to a maximum of four digits, then you could do:

s = "%.4f" % number  # rounds to four decimal places
s = s.rstrip("0")  # ignore trailing zeroes, whether significant or not
count = len(s.split(".")[1])


Assuming all the numbers fit in the range where they are shown in non-
exponential format. If you have to handle numbers like 1.23e19 as well, 
you'll have to parse the string more carefully. (Keep in mind that most 
floats above a certain size are all integer-valued.)


> The numbers are given to me as Python floats; I have no control over
> that.

If that's the case, what makes you think that two floats from the same 
data set were measured to different precision? Given that you don't see 
strings, only floats, I would say that your problem is unsolvable. 
Whether I measure something to one decimal place and get 23.5, or four 
decimal places and get 23.5000, the float you see will be the same.

Perhaps you ought to be using Decimal rather than float. Floats have a 
fixed precision, while Decimals can be configured. Then the right way to 
answer your question is to inspect the number:

py> from decimal import Decimal as D
py> x = D("23.5000")
py> x.as_tuple()
DecimalTuple(sign=0, digits=(2, 3, 5, 0, 0, 0), exponent=-4)

The number of decimal digits precision is -exponent.


> I'm willing to accept that fact that I won't be able to differentiate
> between float("38.0") and float("38.0000").  Both of those map to 1,
> which is OK for my purposes.

That seems... well, "bizarre and wrong" are the only words that come to 
mind. If I were recording data as "38.0000" and you told me I had 
measured it to only one decimal place accuracy, I wouldn't be too 
pleased. Maybe if I understood the context better?

How about 38.12 and 38.1200?

By the way, you contradict yourself here. Earlier, you described 38.0 as 
having zero decimal places (which is wrong). Here you describe it as 
having one, which is correct, and then in a later post you describe it as 
having zero decimal places again.



-- 
Steven D'Aprano
http://import-that.dreamwidth.org/

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#70703

Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:

> By the way, you contradict yourself here. Earlier, you described 38.0 as 
> having zero decimal places (which is wrong). Here you describe it as 
> having one, which is correct, and then in a later post you describe it as 
> having zero decimal places again.

I get the impression that this is at the core of the misunderstanding.
Having a number's representation ending in “….0” does not mean zero
decimal places; it has exactly one. The value's representation contains
the digit “0” after the decimal point, but that digit is significant to
the precision of the representation.

If the problem could be stated such that “38.0” and “38” and “38.000”
are consistently described with the correct number of decimal digits of
precision (in those examples: one, zero, and three), maybe the
discussion would make more sense.

-- 
 \     “Men never do evil so completely and cheerfully as when they do |
  `\        it from religious conviction.” —Blaise Pascal (1623–1662), |
_o__)                                                   Pensées, #894. |
Ben Finney

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#70704

On Tue, 29 Apr 2014 13:23:07 +1000, Ben Finney wrote:

> Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:
> 
>> By the way, you contradict yourself here. Earlier, you described 38.0
>> as having zero decimal places (which is wrong). Here you describe it as
>> having one, which is correct, and then in a later post you describe it
>> as having zero decimal places again.
> 
> I get the impression that this is at the core of the misunderstanding.
> Having a number's representation ending in “….0” does not mean zero
> decimal places; it has exactly one. The value's representation contains
> the digit “0” after the decimal point, but that digit is significant to
> the precision of the representation.
> 
> If the problem could be stated such that “38.0” and “38” and “38.000”
> are consistently described with the correct number of decimal digits of
> precision (in those examples: one, zero, and three), maybe the
> discussion would make more sense.


It's actually trickier than that. Digits of precision can refer to 
measurement error, or to the underlying storage type. Python floats are C 
doubles, so they have 64 bits of precision (approximately 17 decimal 
digits, if I remember correctly) regardless of the precision of the 
measurement. The OP (Roy) is, I think, trying to guess the measurement 
precision after the fact, given a float. If the measurement error really 
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.

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:

py> x = 1234.1  # actual internal is closer to 1234.099999999999909
py> ("%.4f" % x).rstrip('0')
'1234.1'

then count the number of digits after the dot. (This assumes that the 
string formatting routines are correctly rounded, which they should be on 
*most* platforms.) But again, this only gives a lower bound to the number 
of significant digits -- it's at least one, but might be more.


-- 
Steven

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#70744

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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#70746

In article <mailman.9594.1398818045.18130.python-list@python.org>,
 Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:

> in a physics or chemistry class the recommended result is
> 
>    1.1 * 2.2 => 2.4

More than recommended.  In my physics class, if you put down more 
significant digits than the input data justified, you got the problem 
marked wrong.

> (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>

Sterling?  Snort.  K&E was the way to go.

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#70793

On Tue, 29 Apr 2014 20:42:33 -0400, Roy Smith <roy@panix.com> declaimed the
following:

>In article <mailman.9594.1398818045.18130.python-list@python.org>,
> Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
>
>> in a physics or chemistry class the recommended result is
>> 
>>    1.1 * 2.2 => 2.4
>
>More than recommended.  In my physics class, if you put down more 
>significant digits than the input data justified, you got the problem 
>marked wrong.
>
>> (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>
>
>Sterling?  Snort.  K&E was the way to go.

	Math teacher was selling them in my 10th grade... Actually I already
owned a Faber-Castell 57/22 "Business" ruler (which did NOT have the CF/DF
scales set for *PI) and a Pickett N-1010-ES Trig rule.

	I've misplaced the Sterling, but I'm fairly sure it was a deci-trig
log-log model.

	In the last 15-20 years I've added NIB versions of Faber-Castell 1/54
Darmstadt, Pickett N-803-ES Dual-Base Log-Log, Pickett Cleveland Institute
of Electronics N-515-T, and a pair of Sama&Etani/Concise circular pocket
rules (models 200 and 600).

	Heh... I wonder if the VEs would have noticed the CIE rule had lots of
electronics formulas on the back, if I'd taken it to the exam session where
I passed both General and Amateur Extra tests. I couldn't take a calculator
-- all of mine were programmable. But the slide-rule I took was just about
as perplexing to the VEs.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#70804

On 4/30/14 7:02 PM, Dennis Lee Bieber wrote:
>>> Sterling?  Snort.  K&E was the way to go.

    Absolutely, snort.  I still have my K&E (Keuffel & Esser Co. N.Y.); 
made of wood... (when ships were wood, and men were steel, and sheep ran 
scared) ... to get to the S L T scales I have to pull the slide out 
(turn it over) and reinsert it. You're right, the CF and DF scales are 
missing, but the A B scales have the π symbol where it should be (more 
or less).  Mine is the 4058 C model, and you're right... has maths 
equivalents and conversions printed on the back...

> 	I've misplaced the Sterling, but I'm fairly sure it was a deci-trig
> log-log model.

    My high school '74 was the last class to learn the slide-rule using 
the Sterling (we paid a deposit to use the school's). I returned my 
Sterling to the teacher at year-end and got my deposit back. They are 
all probably in an old card-board box in the basement. I should ask.

>
> 	In the last 15-20 years I've added NIB versions of Faber-Castell 1/54
> Darmstadt, Pickett N-803-ES Dual-Base Log-Log, Pickett Cleveland Institute
> of Electronics N-515-T, and a pair of Sama&Etani/Concise circular pocket
> rules (models 200 and 600).

    I received my Pickett Model N4-T Vector-Type Log Log Dual-Base Speed 
Rule as a graduation | birthday gift... off to college with a leather 
cased slip stick hanging from my belt (I was invincable).  Mine had the 
CF/m DF/m scales also -- folded at 2.3, the loge of 10 with π where it 
should be (more or less).  Copyright 1959... that baby was the king of 
slide rules...  I pull it out from time to time, just for warm feelings.

>
> 	Heh... I wonder if the VEs would have noticed the CIE rule had lots of
> electronics formulas on the back, if I'd taken it to the exam session where
> I passed both General and Amateur Extra tests. I couldn't take a calculator
> -- all of mine were programmable. But the slide-rule I took was just about
> as perplexing to the VEs.
>

    I carried my slide rule to my general class exam as well. The VE 
inspected it to be sure that certain stuff was not written in pencil 
between the scales! True story. Its not required today, of course, but I 
can still send/receive at 20 wpm. <sigh>

marcus   W0MHH
'73

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#70805

Mark H Harris <harrismh777@gmail.com> writes:
>    I received my Pickett Model N4-T Vector-Type Log Log Dual-Base
> Speed Rule as a graduation | birthday gift...

There is a nice Javascript simulation of the N4-ES here:

http://www.antiquark.com/sliderule/sim/n4es/virtual-n4es.html

Some other models are also on that site.

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#70806

On 4/30/14 10:56 PM, Paul Rubin wrote:

> There is a nice Javascript simulation of the N4-ES here:
>
> http://www.antiquark.com/sliderule/sim/n4es/virtual-n4es.html
>

Thank you!

The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES 
on the site is yellow (mine is white) and the site rule indicates Picket 
& Eckel Inc. (that's where the E comes from)  Also the the ES states 
Chicage Ill USA where the T states Made in USA.

The only technical difference is the T scale (which is folded-expanded 
on both). On the ES the T scale is listed only once in the margin.  On 
the N4-T the T scale is listed 'twice'!--  once for each part of the 
fold.  Well, that gives (2) scales instead of one --for T...  increasing 
the number of scales on the rule from 34 to 35... if I'm counting right. 
  Which makes the N4-T more valuable... supposedly.  I don't plan are 
parting with it... till I croak, then my son (who is studying 
engineering this fall) will inherit it...  heh   he won't have a clue 
what to do with it !

The simulated rule on the site above is fabulous... especially if viewed 
from a large wide LED.  ... simply fabulouso/    :)



marcus

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#70820

On May 1, 2014, at 12:16 AM, Mark H Harris <harrismh777@gmail.com> wrote:

> On 4/30/14 10:56 PM, Paul Rubin wrote:
> 
>> There is a nice Javascript simulation of the N4-ES here:
>> 
>> http://www.antiquark.com/sliderule/sim/n4es/virtual-n4es.html
>> 
> 
> Thank you!
> 
> The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES on the site is yellow (mine is white) and the site rule indicates Picket & Eckel Inc. (that's where the E comes from)  Also the the ES states Chicage Ill USA where the T states Made in USA.
> 

I’ve resisted - but finally have to jump into this discussion...

Picket used to talk a lot about their yellow background being optimized for the color the human eye was most sensitive to and therefore produced the sharpest focus and allowed the most precise reading of the scales.  Nice theory, but at least on MY Picket rule the scales were printed not engraved and the result negated any possible advantage the color might have given.

I’m surprised no one has jumped in to defend/tout the Dietzgen slide rules (which I always thought were the ultimate).  Mine (their Vector Log Log) is one of their Microglide series that had teflon rails inserted in the body and is still totally stick-free after nearly 50 years.

Taking it one step further, I _ALSO_ have a Curta Type II calculator http://en.wikipedia.org/wiki/Curta_calculator - which still operates as smoothly as it did the day I bought it.

-Bill

> The only technical difference is the T scale (which is folded-expanded on both). On the ES the T scale is listed only once in the margin.  On the N4-T the T scale is listed 'twice'!--  once for each part of the fold.  Well, that gives (2) scales instead of one --for T...  increasing the number of scales on the rule from 34 to 35... if I'm counting right.  Which makes the N4-T more valuable... supposedly.  I don't plan are parting with it... till I croak, then my son (who is studying engineering this fall) will inherit it...  heh   he won't have a clue what to do with it !
> 
> The simulated rule on the site above is fabulous... especially if viewed from a large wide LED.  ... simply fabulouso/    :)
> 
> 
> 
> marcus
> -- 
> https://mail.python.org/mailman/listinfo/python-list

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#70977

On 5/1/14 10:53 AM, William Ray Wing wrote:
> I’m surprised no one has jumped in to defend/tout the Dietzgen slide rules
> (which I always thought were the ultimate).  Mine (their Vector Log Log) is
> one of their Microglide series that had teflon rails inserted in the body
> and is still totally stick-free after nearly 50 years.
>

http://www.marksmath.com/slide-rules/img/ed-n1725.jpg

The above link is nice for the Dietzgen Microglide. It doesn't have the 
CF/m DF/m scales, but is a very nice Vector type log log. Most of my 
drafting equipment from the same era was Dietzgen; it looked like the 
previous video post featured the same/

My dad has one of these; but I can't get him to part with it yet...



marcus

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#70835

On Wed, 30 Apr 2014 23:16:17 -0500, Mark H Harris <harrismh777@gmail.com>
declaimed the following:

>On 4/30/14 10:56 PM, Paul Rubin wrote:
>
>> There is a nice Javascript simulation of the N4-ES here:
>>
>> http://www.antiquark.com/sliderule/sim/n4es/virtual-n4es.html
>>
>
>Thank you!
>
>The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES 
>on the site is yellow (mine is white) and the site rule indicates Picket 
>& Eckel Inc. (that's where the E comes from)  Also the the ES states 
>Chicage Ill USA where the T states Made in USA.

	ES was for "Eye-Saver" -- the yellow background vs the bright white of
the other models.

	For the audience who might be interested...
http://www.sphere.bc.ca/test/sruniverse.html
(The N515T is available for $95)
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#70965

On 5/1/14 9:06 PM, Dennis Lee Bieber wrote:
>> The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES
>> on the site is yellow (mine is white) and the site rule indicates Picket
>> & Eckel Inc. (that's where the E comes from)  Also the the ES states
>> Chicage Ill USA where the T states Made in USA.
>
> 	ES was for "Eye-Saver" -- the yellow background vs the bright white of
> the other models.

    Actually, I think you're right. I never used the a yellow rule, but 
I will say that my N4-T never caused me any eye-strain (but I was 
younger then).

    The N4-T was a flat white also... very easy to read.  I really don't 
know what all the 'yellow' hype was all about.

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#70970

On Tue, 06 May 2014 09:51:25 -0500, Mark H Harris wrote:

> On 5/1/14 9:06 PM, Dennis Lee Bieber wrote:
>>> The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES
>>> on the site is yellow (mine is white) and the site rule indicates
>>> Picket & Eckel Inc. (that's where the E comes from)  Also the the ES
>>> states Chicage Ill USA where the T states Made in USA.
>>
>> 	ES was for "Eye-Saver" -- the yellow background vs the bright 
white of
>> the other models.
> 
>     Actually, I think you're right. I never used the a yellow rule, but
> I will say that my N4-T never caused me any eye-strain (but I was
> younger then).
> 
>     The N4-T was a flat white also... very easy to read.  I really don't
> know what all the 'yellow' hype was all about.

probably about $XX.XX more :-) (before my time so I would not have a clue 
about the actual cost)



-- 
If you don't do the things that are not worth doing, who will?

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#70975

[Multipart message — attachments visible in raw view] — view raw

HP 35. $350 in 1973 or 4. Still have it somewhere.  Tom yay!
On May 6, 2014 11:20 AM, "alister" <alister.nospam.ware@ntlworld.com> wrote:

> On Tue, 06 May 2014 09:51:25 -0500, Mark H Harris wrote:
>
> > On 5/1/14 9:06 PM, Dennis Lee Bieber wrote:
> >>> The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES
> >>> on the site is yellow (mine is white) and the site rule indicates
> >>> Picket & Eckel Inc. (that's where the E comes from)  Also the the ES
> >>> states Chicage Ill USA where the T states Made in USA.
> >>
> >>      ES was for "Eye-Saver" -- the yellow background vs the bright
> white of
> >> the other models.
> >
> >     Actually, I think you're right. I never used the a yellow rule, but
> > I will say that my N4-T never caused me any eye-strain (but I was
> > younger then).
> >
> >     The N4-T was a flat white also... very easy to read.  I really don't
> > know what all the 'yellow' hype was all about.
>
> probably about $XX.XX more :-) (before my time so I would not have a clue
> about the actual cost)
>
>
>
> --
> If you don't do the things that are not worth doing, who will?
> --
> https://mail.python.org/mailman/listinfo/python-list
>

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#70991

On Tue, 06 May 2014 09:51:25 -0500, Mark H Harris <harrismh777@gmail.com>
declaimed the following:

>On 5/1/14 9:06 PM, Dennis Lee Bieber wrote:
>>> The N4-ES and the N4-T (mine) are essentially the same rule. The N4-ES
>>> on the site is yellow (mine is white) and the site rule indicates Picket
>>> & Eckel Inc. (that's where the E comes from)  Also the the ES states
>>> Chicage Ill USA where the T states Made in USA.
>>
>> 	ES was for "Eye-Saver" -- the yellow background vs the bright white of
>> the other models.
>
>    Actually, I think you're right. I never used the a yellow rule, but 
>I will say that my N4-T never caused me any eye-strain (but I was 
>younger then).
>
	T was "Traditional" (ie; black on white)

>    The N4-T was a flat white also... very easy to read.  I really don't 
>know what all the 'yellow' hype was all about.

	Same thing as yellow chalk on a green board, vs white chalk on a black
board... Less extreme brightness levels, focusing on where the eye is most
sensitive (yellow-green)
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#70811

In article <ljsghc$65b$1@speranza.aioe.org>,
 Mark H Harris <harrismh777@gmail.com> wrote:

>     Absolutely, snort.  I still have my K&E (Keuffel & Esser Co. N.Y.); 
> made of wood... (when ships were wood, and men were steel, and sheep ran 
> scared) ... to get to the S L T scales I have to pull the slide out 
> (turn it over) and reinsert it. You're right, the CF and DF scales are 
> missing, but the A B scales have the π symbol where it should be (more 
> or less).  Mine is the 4058 C model, and you're right... has maths 
> equivalents and conversions printed on the back...

For those who have no idea what we're talking about, take a look at 
http://www.ted.com/talks/clifford_stoll_on_everything.  If you just want 
to see what you do with a slide rule, fast forward to 14:20, but you 
really owe it to yourself to invest the 18 minutes to watch the whole 
thing.

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#70822

On 05/01/2014 05:56 AM, Roy Smith wrote:
> In article <ljsghc$65b$1@speranza.aioe.org>,
>   Mark H Harris <harrismh777@gmail.com> wrote:
>
>>      Absolutely, snort.  I still have my K&E (Keuffel & Esser Co. N.Y.);
>> made of wood... (when ships were wood, and men were steel, and sheep ran
>> scared) ... to get to the S L T scales I have to pull the slide out
>> (turn it over) and reinsert it. You're right, the CF and DF scales are
>> missing, but the A B scales have the π symbol where it should be (more
>> or less).  Mine is the 4058 C model, and you're right... has maths
>> equivalents and conversions printed on the back...
>
> For those who have no idea what we're talking about, take a look at
> http://www.ted.com/talks/clifford_stoll_on_everything.  If you just want
> to see what you do with a slide rule, fast forward to 14:20, but you
> really owe it to yourself to invest the 18 minutes to watch the whole
> thing.
>

Anyone (besides me) ever seen a cylindrical slide rule?  I have one -- unfortunately misplaced 
at the moment.  :-(

The scales were helical around a cylinder giving (it was claimed) to be the equivalent of a 
five-foot rule.  But that still only gave one additional significant digit.  Only two scales, 
however, which limited its use to multiply/divide and logs.  But interesting.

I just did a quick google search and found a picture of one on e-bay, asking price of $175. 
This price rather surprised me because when I bought mine new (probably 45 or so years ago) I'm 
sure I didn't pay more than around $25-$30 for it.  And mine is in far better condition than the 
one in the e-bay photo.  I recently ran across mine, but promptly misplaced it again (long story 
-- don't ask...).  I'll have to look for it again.  (And no, mine is not for sale when/if I find 
it again.)

      -=- Larry -=-

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#70827

On 2014-05-01, Larry Hudson wrote:

> On 05/01/2014 05:56 AM, Roy Smith wrote:

>> For those who have no idea what we're talking about, take a look at
>> http://www.ted.com/talks/clifford_stoll_on_everything.  If you just want
>> to see what you do with a slide rule, fast forward to 14:20, but you
>> really owe it to yourself to invest the 18 minutes to watch the whole
>> thing.
>>
>
> Anyone (besides me) ever seen a cylindrical slide rule?  I have one -- unfortunately misplaced 
> at the moment.  :-(
>
> The scales were helical around a cylinder giving (it was claimed) to be the equivalent of a 
> five-foot rule.  But that still only gave one additional significant digit.  Only two scales, 
> however, which limited its use to multiply/divide and logs.  But interesting.

I have a "circular" (really spiral) slide rule that I inherited from
my grandfather.

http://www.ducksburg.com/atlas_slide_rule/

One of my uncles told me that he took it (or a similar model) to
university (ca. 1960, I guess) & got an F on a calculus test because
his answers were too accurate & precise to be honest.  He went to the
professor's office, showed him the circular slide rule, & got an A.


-- 
To live without killing is a thought which could electrify the world,
if men were only capable of staying awake long enough to let the idea
soak in.                                             --- Henry Miller

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