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

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

Subject |
st: RE: How to know how a global macro was generated: -smr- as an example |

Date |
Thu, 11 Dec 2008 21:39:23 -0000 |

I guess I lay down the law on what is, and what is not, good practice so frequently that I should be the last one to demur about somebody else doing that. But I don't accept, personally, that all users who write Stata software have an obligation to explain the formulae they use, even indirectly by referencing. That is Utopian and impractical. (What if the references I give do not explain all the ideas that I use, which will be very common?) That aside, one good practice not followed here is to explain where the (user-written) code discussed comes from. STB-29 sg29.1 . . . Tabulation of observed/expected ratios & conf. intervals (help smrby if installed) . . . . . . . . . . . . . . . . . P. Sasieni 1/96 pp.21--24; STB Reprints Vol 5, pp.87--90 improved version of smr Looking at -smrby- I note that 1. -smrby- itself does not define any globals. 2. Just before they are used, -smrby- calls -_crccip-. 3. _crccip.ado is part of the Stata distribution. Commands whose names begin with _crc are short utilities written by the Stata developers. (CRC is the abbreviation for the original name of StataCorp.) 4. So look inside _crccip.ado. Nick n.j.cox@durham.ac.uk Tiago V. Pereira Not rarely I almost drive myself crazy because several Stata commands fail to provide info about the formulations they use to compute variances/standard errors in their calculations. I have already claimed that most Stata packages should provide references on their formulae/and or to point out where we can get detailed info on the methods implemented. When no reference is given, I usually open the code and see how it was calculated, trying to find ou in textbooks similar formulations. However, in the case of the -smrby- command, which calculates the ratio of OBSERVED/EXPECTED counts and its confidence intervals, I could not figure out how the global macros S_1 and S_2 were computed. Once you can rapidly take a look on the code of the -smr- command, I did not paste the whole code here for simplicity. Specifically, I am interested in the following lines: if _rc==0 { _crccip `o' `level' local l=100*($S_1/`e') local u=100*($S_2/`e') local r=100*(`o'/`e') local emark "" } I will be really grateful for any tip on how both $S_1 and $S_2 were calculated. * * 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/

**References**:**st: How to know how a global macro was generated: -smr- as an example***From:*"Tiago V. Pereira" <tiago.pereira@incor.usp.br>

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