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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: How to check if observation of a particular variable value exists? If not, create that observation. |

Date |
Tue, 29 May 2012 10:19:30 +0100 |

If it is really a case of whether you have four records (Stata terminology is "observations"), you don't need a program, but just to work in the Editor. But I guess your real problem is more substantial. Look at the help for -fillin-. This version of your code should work qui forvalues i = 1/2 { forvalues j = 1/2 { count if A == `i' & B == `j' if r(N) == 0 { set obs `=_N + 1' replace A = `i' in L replace B = `i' in L } } } It is best not to use "missing" to mean "not present". Missing in Stata usually means that a value is missing. Nick On Tue, May 29, 2012 at 10:09 AM, Ran Gu <lionup@gmail.com> wrote: > Suppose I have a data with 2 variables, say A and B, both with values > 1 and 2. The data are sorted by A and B. Then there should be 4 > records: (A=1 B=1) (A=1 B=2) (A=2 B=1) (A=2 B=2) > > Suppose I don't know whether the 4 observations are all exist or not. > How could I check that in a do file? > Then, If a record is missing, say (A=1 B=1), I would like to create it. > > for example: > forvalues i = 1/2 { > forvalues j = 1/2 { > if obs with A == `i' and B == `j' is missing { > local new = _N+1 > set obs `new' > replace A == `i' if _n==`new' > replace B == `j' if _n==`new' > } > } > } > * * 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: How to check if observation of a particular variable value exists? If not, create that observation.***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: How to check if observation of a particular variable value exists? If not, create that observation.***From:*Ran Gu <lionup@gmail.com>

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