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From |
wgould@stata.com (William Gould, Stata) |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Significant figures formats |

Date |
Fri, 18 Jul 2003 11:19:17 -0500 |

Roger Newson <roger.newson@kcl.ac.uk> wrote, > I have been looking in -[U] 15.5 Formats: controlling how data are > displayed-, but I cannot seem to find any formats for displaying data to k > significant figures, except for the %w.de formats, which display data in the > form x.ye-z. Ideally, if I have a data set with 1 observation per estimated > parameter and data on confidence intervals and P-values, then I would like > to be able to list the P-values to 2 significant figures, so that 4.5e-1 > would be listed as 0.45 and 4.5e-2 would be listed as 0.045 and 4.5e-5 would > be listed as 0.000045 With Stata 8, try %9.2g, %8.2g, or %<w>.2g: . display %9.2g 4.52394e-3 .0045 . display %9.2g 4.52394e-5 .000045 Display value x with %<w>.<d>g, with d!=0, does not display significant figures, but for |x|<1, it does. Let me repeat something I wrote on 7apr2003: ------------------------------------------------------------------------------ I would like to mention the new-to-Stata-8 %<w>.<d>g and %<w>.<d>gc formats when <d> is greater than 0. I am not certain many of you noticed the change. %12.0g, as you know, shows a number in field of width 12. That number is displayed in such away as to show as many of its digits as possible. ----+----1----+----2 3.141592654 <- display %12.0g _pi 31.41592654 <- display %12.0g _pi*10 314159.2654 <- display %12.0g _pi*10^5 314159265.4 <- display %12.0g _pi*10^8 3141592654 <- display %12.0g _pi*10^9 3.14159e+10 <- display %12.0g _pi*10^10 3.141592654 <- display %12.0g _pi .3141592654 <- display %12.0g _pi*10^(-1) .0003141593 <- display %12.0g _pi*10^(-4) .0000314159 <- display %12.0g _pi*10^(-5) 3.14159e-06 <- display %12.0g _pi*10^(-6) I want to draw you attention especially to that last two lines: .0000314159 3.14159e-06 Note how smart is %12.0g. It could have displayed _pi*10^(-6) as .0000031415 but it knew that, if it switched to %e format, it could display an extra digit, and so it did. That's the purpose of the %g format: to show as many digits as possible within the specified width. New to Stata 8, you can specify the maximum number of digits you want, which you specify as the <d> in %<w>.<d>g: ----+----1----+----2 3.142 <- display %12.4g _pi 31.42 <- display %12.4g _pi*10 3142 <- display %12.4g _pi*10^3 314159 <- display %12.4g _pi*10^5 31415927 <- display %12.4g _pi*10^7 3141592654 <- display %12.4g _pi*10^9 3.142e+10 <- display %12.4g _pi*10^10 3.142 <- display %12.4g _pi .3142 <- display %12.4g _pi*10^(-1) .0003142 <- display %12.4g _pi*10^(-4) .00003142 <- display %12.4g _pi*10^(-5) 3.1412e-06 <- display %12.4g _pi*10^(-6) %12.4g is almost a 4-significant digit format, the exceptions being 314159 <- display %12.4g _pi*10^5 31415927 <- display %12.4g _pi*10^7 3141592654 <- display %12.4g _pi*10^9 To show those with 4 digits would have required either going to %e format: 3.1412e+05 3.1412e+07 3.1412e+09 or rounding and padding the numbers with zeros 314200 31420000 3142000000 The %w.dg, d>0, format assumes you do not want either of those solutions. If you wanted the %e format, you can use the %e format at the outset. We thought about implementing the round-and-pad solution, but came to the conclusion that researchers don't want that. As long as digits are going to be displayed, one might as well put the actual digit in each position. If there is an interest in the round-and-pad solution, we would be willing to implement a %G format to go along with %g. ------------------------------------------------------------------------------ -- Bill wgould@stata.com * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: Re: Significant figures formats***From:*Roger Newson <roger.newson@kcl.ac.uk>

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