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

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

Subject |
st: RE: Is there a quick way of customizing linear interpolation? |

Date |
Thu, 22 Jul 2010 18:45:48 +0100 |

-ipolate- with -if- is, I guess, not the answer here. I think you can hardly include all you want and exclude all you want. A better answer is 1. -ipolate- any way. 2. Identify spells of missing values and reverse the -ipolate- of missings for spells of three or more missings. -tsspell- from SSC is one tool for this. You explain your problem clearly but don't say much about your data. How to use -tsspell- from SSC for #2 depends on your set-up. Here are three examples. (a) Data are in sequence, but no time variable or panel identifier. gen long time = _n * continue with code for (b) (b) A time variable is defined, but no panel identifier. tsset time ipolate oldvar time, gen(newvar) tsspell , cond(missing(oldvar)) egen length = max(_seq), by(_spell) replace newvar = . if length > 2 (c) A time variable and panel identifier. tsset id time by id: ipolate oldvar time, gen(newvar) tsspell, cond(missing(oldvar)) egen length = max(_seq), by(id _spell) replace newvar = . if length > 2 See also 1. -cipolate- and -csipolate- from SSC. 2. dm0029 . . . . . . . . . . . . . . Speaking Stata: Identifying spells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox Q2/07 SJ 7(2):249--265 (no commands) shows how to handle spells with complete control over spell specification (FYI, "wanna" remains valleyspeak, not correct English!) Nick n.j.cox@durham.ac.uk Halit Akturk I am a Stata 11 user. Is there any way to customize ipolate command in Stata in a quick way? I like to do linear interpolation but I have a constraint. I like to fill in the missing observations as long as the missing observations happen at most 2 times consequtively. For instance, say I have the following data where "." stands for missing observation: 1, 4, 5, ., 7, ., ., ., 9, ., ., 15. The usual Stata's ipolate gives: 1, 4, 5, 6, 7, 7.5, 8, 8.5, 9,11, 13, 15. The ipolate will fill in all of the missing observations. I don't wanna do that. I like to fil in the missing values as long as they are at most 2 observations consequtively. So the customized linear interpolation (which is what I am looking for) should give me the following result: 1, 4, 5, 6, 7, ., ., ., 9, 11, 13, 15. I hope I explained what I am looking for well. * * 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: Is there a quick way of customizing linear interpolation?***From:*Halit Akturk <halitakturk@gmail.com>

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