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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: Keeping trailing zeros when formatting a decimal |

Date |
Thu, 1 Oct 2009 19:00:09 +0100 |

This generated a lively thread. (Oddly enough, although I still remember teachers stressing the idea of sig.fig. -- as it was called where I grew up -- in practice I always want to program display with either Stata's defaults or a fixed number of decimal places.) My one contribution is slightly oblique. If existing formats don't suit, it seems a better strategy to drill down and try first principles. 1. Significant figures can be got from the fractional part of the base 10 logarithm of whatever it is. . di round(10 * 10^mod(log10(.123456789), 1)) 12 . di round(10 * 10^mod(log10(123456789), 1)) 12 -- with different prefactors as desired. 2. Multiplying powers can be got from the integer part of same. . di floor(log10(123456789)) 8 . di floor(log10(.123456789)) -1 3. Logically it seems that's all the information you need to work out leading and trailing zeros, except that if there's a negative sign you have to strip it off first and put it back again. I haven't tried to understand Roy Wada's program, which at heart should be equivalent to this. No doubt the help file will document that it also deals with complications that I have missed. Nick n.j.cox@durham.ac.uk Miranda Kim I would be very grateful for advice on the following basic formatting questions... To store a number as a string with a format showing 2 significant figures, I do the following, for example: di "`=string(-0.000029, "%9.2g")'" If the second significant figure is a zero, how can I make sure this is still displayed? The following produces: . di "`=string(-0.0000201, "%9.2g")'" -.00002 when I want it to display "-0.000020" Also, how can I make sure it displays the zero before the decimal point? Also, why does . di "`=string(-0.000029, "%9.1g")'" -.000029 not show only 1 significant figure? * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: RE: Keeping trailing zeros when formatting a decimal***From:*Roy Wada <roywada@hotmail.com>

**RE: st: RE: Keeping trailing zeros when formatting a decimal***From:*Roy Wada <roywada@hotmail.com>

**References**:**st: Keeping trailing zeros when formatting a decimal***From:*Miranda Kim <mk@mrc.soton.ac.uk>

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