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I understand that this is not strictly a TeX question but I have recently been asked to correct an equation presented as the first example in the image below to that of the second example i.e., to use the thousands separator. I compromised by typesetting the third example with a \thinspace as the thousands separator.

enter image description here

All three types are allowed in SI units. What would you recommend? Is there a canonical way?

Edit

I came across a paper by Knuth, where large number coefficients are used.

enter image description here

He clearly is in favour of not using any separators or spaces. This fact, besides his own papers is corroborated by an anecdote described in Mathematical Writing (page 53), regarding an article he submitted to the ACM.

[...] where Don wrote 1000000 they substituted 1,000,000. Don objected that although this might be justifed in text, his use is perfectly OK in a formula. Well then, they replied, write 106 Fine, said, Don, but what do I do when the number is 1234567? The IEEE standard here is to insert spaces, thus: 1 234 567. Don doesn't like this in formulae, but agrees that it may be useful in a high precision context, such as numerical tables.

For me that settles it!

lockstep
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yannisl
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    from mathematical typesetting completely without additional space. –  Jan 26 '11 at 19:16
  • @Herbert Traditionally we would not separate them, hence my choice. The counter-argument was that there is no valid reason not to and that it improves readability. Steven G. Krantz in Handbook of Typography for the Mathematical Sciences is silent about this. – yannisl Jan 26 '11 at 19:23
  • Are you using the \num macro from the siunitx package? – las3rjock Jan 26 '11 at 19:25
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    If you were to go for the middle version (commas), at least use {,} rather than the bare comma. That will fix the rather glaring problem with spacing. Personally, I lean toward the thin space solution, even in mathematics, at least if the numbers have nine digits or more. But I might be tempted to break with tradition and put them in groups of five rather than three. – Harald Hanche-Olsen Jan 26 '11 at 19:28
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    @Yannis: you want to show an approximation of a function, the reason why it is not important for the reader how large a number may be, important is only how the number is build; the definition of erf^{-1} as a sum is more of interest to the reader –  Jan 26 '11 at 19:35
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    Looking through the maths course I'm currently doing (OU M373: Optimisation), large numbers are divided up in SI style 0.123 456, with what look like thin spaces. However, that is in tables rather than in equations, at least that I've found so far. – Joseph Wright Jan 26 '11 at 20:31
  • In french, we use a thin space, I get it with \numprint{...} or \np{...} with the package numprint.sty. numprint works with babel. – Alain Matthes Jan 26 '11 at 23:02
  • @Harald Would you please put your comment in an answer? I would like to accept it. – yannisl Jan 27 '11 at 06:36
  • @Yiannis: Sure. – Harald Hanche-Olsen Jan 27 '11 at 09:41
  • @Herbert: I agree; numbers with that many significant digits should only be used for measurements or numerical results. The number 182476800 is quite insignificant in this case, it is more interesting how it is calculated. – Philipp Jan 27 '11 at 14:20
  • possible duplicate of What commands are there for horizontal spacing? – Cole Tobin Jun 21 '14 at 18:29
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    @ColeJohnson Huh? Not really and how can you this is a duplicate of a question asked one year later than this one? Why not the other way round. – yannisl Jun 22 '14 at 01:06

2 Answers2

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If you were to go for the middle version (commas), at least use {,} rather than the bare comma. That will fix the rather glaring problem with spacing. Personally, I lean toward the thin space solution, even in mathematics, at least if the numbers have nine digits or more. But I might be tempted to break with tradition and put them in groups of five rather than three.

Harald Hanche-Olsen
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Your question rely upon your country's mathematics typesetting triditional habbit, and it is not a TEX problem. Anyway, You could input

\frac{\pi^2}{123\thousandsymbol 456}

to get diffrence output easily. If your codes had been finished, the better way (as far as I know) to modify them is using regular expression, adding the command inside digits (on reverse order).

luochaodong
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