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From |
"Ben Hoen" <bhoen@lbl.gov> |

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

Subject |
RE: st: conditional merging |

Date |
Wed, 7 Nov 2012 10:37:37 -0500 |

Thanks Nick. I am not sure there is a standard way that these "condition" values trend over time across the whole dataset, and therefore interpolating them might not be appropriate. Moreover, for each home, there might not be many data points. Finally, the values that are allowable for condition are discreet (non-continuous), and therefore would complicate a linear, cubic, cubic spline process (though, of course that could be dealt with by using .=int(x) ). Would the interpolation allow me to take into account all of these characteristics? For, in part, this reason, I was hoping to find some way to execute a "conditional merge" (again, my words). Additionally, the process of learning how one might do it with this "condition" data, could be applied to extracting other characteristic data that are also only present sporadically across time (e.g., size of the home) but that also might periodically change (e.g., the home might be added to). Is there a way to use if/then statements in a merge process? Ben Ben Hoen LBNL Office: 845-758-1896 Cell: 718-812-7589 -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox Sent: Tuesday, November 06, 2012 6:47 PM To: statalist@hsphsun2.harvard.edu Subject: Re: st: conditional merging Carry forward can be as little as one line of code: see FAQ . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox 2/03 How can I replace missing values with previous or following nonmissing values? http://www.stata.com/support/faqs/data-management/replacing-missing-values/ I don't see that this is an imputation problem at all. It calls for interpolation. Indeed, have you considered some kind of interpolation, say linear, cubic, cubic spline? On Tue, Nov 6, 2012 at 7:33 PM, Ben Hoen <bhoen@lbl.gov> wrote: > I have two files sales.dta and condition.dta. sales.dta has two variables > (home_id saleyear), and condition.dta has three variables (home_id > inspection_year condition). The variable inspection_year can take the vales > of 2000-2011 for any home but for many homes only some years are present (in > many years the home was not inspected. Therefore a sample of the data might > look like: > > home_id inspection_year condition > 50121 2002 4 > 50121 2006 4 > 50121 2011 3 > 50681 2004 2 > 50681 2010 3 > 51040 2006 2 > 51040 2010 2 > 51040 2011 3 > > I would like to populate the sales.dta file with the condition of the parcel > in the inspection_year that is the closest to, but not following the > sale_year. > > So, for example, the following dataset would result > > home_id sale_year condition > 50121 2007 4 > 50121 2011 3 > 50681 2008 2 > 51040 2003 . > 51040 2010 3 > > I know I am not the first person to have this problem, but could not find > threads on this. Maybe I am using the wrong search terms. Any help would > be greatly appreciated. > > (As I wrote this I realized one not as elegant work-around would be to > fill-in missing data for each missing year in the condition.dta file, > potentially using the user-written "carryforward" or even imputing the data > using, e.g., mi impute, and then matching home_id sale_year to home_id > inspection_year.) * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: conditional merging***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: conditional merging***From:*"Ben Hoen" <bhoen@lbl.gov>

**Re: st: conditional merging***From:*Nick Cox <njcoxstata@gmail.com>

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