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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Column vector into variable, accounting for -marksample- |

Date |
Mon, 8 Oct 2012 00:46:05 +0100 |

I would use Mata in most such cases, but for this problem in Stata I would go tempvar obsno gen `obsno' = _n marksample `touse' replace `touse' = -`touse' sort `touse' `obsno' Then the first so many observations in the dataset are also the first so many being used in the program and so those to receive the values of the vector. That is, `touse' is created 0 and 1 but if negated is 0 and -1; -sort `touse'- then puts the observations being used first. Negation makes no difference to the consequence of doing things -if `touse'-. Nick On Sun, Oct 7, 2012 at 8:45 PM, Lacy,Michael <Michael.Lacy@colostate.edu> wrote: > I have a Stata program that obtains a column vector, say r(X) by calling another program. I want to put the > values of r(X) into a variable in the original dataset, which for me is complicated by -marksample-. > > The values of r(X) arrive in the same order as the original data would be if cases not selected by > -marksample- were dropped. So, if were there no use of marksample, the row index of r(X) would > correspond to _n, and there would be no difficulty; -svmat- will align the contents of r(X) as desired. > But this is not true because the data are processed -if `touse'-, so that the first element of r(X) might > correspond to the 4th observation of the original data set, the second element to the 7th observation, > and so forth. > > My thinking so far involves reconstructing the r(X) matrix into another matrix, putting in missing values > as indicated by -touse-, per my fragment below. Is there a less lunky way to accomplish this? > (My program might be called many times in a simulation context, so time is an issue.) > > This must be an utterly commonly task. (And yes, I could do the same in Mata, but it's still more > or less the same thing.) > > program whatever > syntax ...[if] ... > marksample touse > > ....Other program is called with if `touse', which returns r(X) > // Make r(X) into a variable > X = return(X) > mkmat `touse', matrix(tu) > mat `temp' = J(`=_N',1,.) // working matrix for repacking X > local pos = 1 > forval i = 1/`=_N' { > if (tu[`i',1] == 1) { > mat `temp'[`i',1] = `D'[`pos',1] > local ++pos > } > } > svmat `temp', name(Xvar) > * * 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/

**References**:**st: Column vector into variable, accounting for -marksample-***From:*"Lacy,Michael" <Michael.Lacy@colostate.edu>

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