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From |
"Martin Weiss" <martin.weiss1@gmx.de> |

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

Subject |
st: AW: What's the added value of having -in- subset the data before -if- does? |

Date |
Wed, 4 Feb 2009 17:01:33 +0100 |

<> ************* bys for: list if foreign &_n<=10 ************* HTH Martin -----Ursprüngliche Nachricht----- Von: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Dan Blanchette Gesendet: Mittwoch, 4. Februar 2009 16:28 An: statalist@hsphsun2.harvard.edu Betreff: st: What's the added value of having -in- subset the data before -if- does? Have you ever wanted to list a selection of observations based on a condition but only list say a subset of 10 obs of that condition? If so, perhaps you've been frustrated with the fact that: . sysuse auto . list if foreign == 1 in 1/10 lists no observations because in the first 52 observations foreign == 0. The -in- subsets the data before the -if- condition subsets the data. This is the opposite in SAS: /* WHERE subsets the data before OBS subsets the data */ PROC PRINT DATA= SASHELP.SHOES(WHERE=(STORES < 10) OBS = 10); RUN; So, the above code lists the first 10 observations where (STORES < 10). I can't think of any situation where I would want to know how many times a certain condition exists in the first X observations. Do others ever need to know that? I figured out a solution where Stata will subset the data to the condition and then only list the range of observations I'm interested in: . list if sum((foreign == 1)) <= 10 The "(foreign == 1)" inside the sum() creates a value equal to 1 when the condition is true and then sum() creates a running sum of that. You can use the sum() function to subset your data for other Stata commands. You could get a range of observations as well: . list if inrange(sum((foreign == 1)),2,11) I may decide always to use this since: . list if sum((foreign == 1)) <= 100 will also work despite the fact there aren't 100 observations in the data. I'll never again get the error message: Obs. nos. out of range r(198); My previous solution was to: preserve keep if foreign == 1 local nobs = 10 if _N < `nobs' local nobs = _N list in 1/`nobs' restore Thoughts? Dan Blanchette Research Associate Center of Entrepreneurship and Innovation Duke University's Fuqua School of Business Durham, NC USA dan.blanchette@duke.edu * * 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/ * * 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: What's the added value of having -in- subset the data before -if- does?***From:*Dan Blanchette <dan.blanchette@duke.edu>

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