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From |
A Loumiotis <antonis.loumiotis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Multiple imputation: conditional option using categorical variables |

Date |
Tue, 1 Oct 2013 08:57:28 +0300 |

Hi Martijn, No, it still works but as I noted in my previous message you have to make sure that you set price to the pre-determined value whenever the condition does not hold. In this case you have to set price to zero whenever inlist(rep78,2,3) before running -ice-. Here is the modified code: *** Example starts sysuse auto, clear set seed 12345678 replace rep78=. if runiform()<.1 replace price=. if runiform()<.1 replace price=0 if inlist(rep78,2,3) replace price=. if rep78==. ice m.rep78 price mpg, cond(price:inlist(rep78,1,4,5)) saving(catexam,replace) use catexam, clear sort _mi _mj browse *** Example ends Hope this helps, Antonis On Mon, Sep 30, 2013 at 5:47 PM, Hogerbrugge, M.J.A. (Martijn) <M.J.A.Hogerbrugge@uu.nl> wrote: > Dear Antonis, > > The following error is returned by -ice-: > > Imputing Error: variable marstat_time2 has >1 value outside subgroup inlist(marstat_time1,1,.) > r(499); > > In your example, the error would also show up if you change the condition from inlist(rep78,1,2,4,5) into inlist(rep78,1,4,5), for example. > Do you have any idea how to work around this issue? > > Kind regards, > Martijn > > >>What exactly is the error that -ice- returns? Could you please >>specify the complete -ice- command that returns that error that you >>mentioned? >> >>Here is a nonsensical example that works. In this example price is >>only answered if categorical variable rep78 is not equal to 3. Not >>that I set price to missing whenever rep78 is missing and equal to >>zero (pre-determined value) whenever rep78 is equal to 3. >> >>*** Example starts >>sysuse auto, clear >>set seed 12345678 >>replace rep78=. if runiform()<.1 >>replace price=. if runiform()<.1 >>replace price=0 if rep78==3 >>replace price=. if rep78==. >>ice m.rep78 price mpg, cond(price:inlist(rep78,1,2,4,5)) saving(catexam,replace) >>use catexam, clear >>sort _mi _mj >>browse >>*** Example ends >> >>As you can see whenever rep78 is imputed to 3, -ice- automatically >>assigns to price the pre-determined value of 0. >> >>Going back to my November 2010 unanswered post about the conditional >>option and categorical variables it is clear now to me that the first >>specification is the appropriate one. Thanks for reminding me about >>this post. I will try to find it and bring a closure to it. >> >>-ice- is a user written program that can be found at >>http://www.ucl.ac.uk/~ucakjpr/. >> >>Best, >>Antonis >> >>On Sat, Sep 28, 2013 at 1:29 PM, Hogerbrugge, M.J.A. (Martijn) >><M.J.A.Hogerbrugge@uu.nl> wrote: >>> Dear Stata users, >>> >>> Does anybody know how to use the "conditional"-option for categorical variables in multiple imputation using >ICE? >>> >>> The help file only provides an example using a dichotomous conditional variable ("female"). In that case, >imputation on a particular variable is only performed if the condition is met (for instance "female == 1"). If the >condition is false, a pre-determined value is imputed. To work correctly, the cases for which the condition is false >need to have only one value on the variable that needs to be imputed. If more than one value is observed, ICE >returns an error. >>> >>> In some instances, however, it is perfectly sensible to have multiple values in the variable to be imputed (for the >observations for which the condition is false). Let me provide a quick example using the variable marital status: >>> - the categories for marital status are [1] "married", [2] "divorced", and [3] "widowed" >>> - marital status is observed at multiple time points >>> - once a person is divorced or widowed, he or she remains so for the remainder of the observation points >>> - the ICE command will look like this: >>> >>> .conditional(marstat_time2: if inlist(marstat_time1,1,.)) >>> .conditional(marstat_time3: if inlist(marstat_time2,1,.)) >>> .conditional(marstat_time4: if inlist(marstat_time3,1,.)) >>> >>> and so on. >>> >>> Thus, marital status at a later time point is not imputed if the case was either divorced or widowed at the >previous time point (i.e., not married [1] or missing [.]). >>> >>> Unfortunately, ICE returns an error for the reason described earlier. Is there some way to be able to do this kind >of conditional imputation nonetheless? I tried looking for previous posts on a similar issue, and found one >(http://www.stata.com/statalist/archive/2010-11/msg00708.html), but this post seems to be never been answered. >>> >>> BTW, I also looked into Stata's own imputation command (MI impute), but the conditional option is implimented >in a similar way, and switching commands seems not to be a way to overcome this problem. >>> >>> Looking forward to your responses and help. >>> ~Martijn Hogerbrugge > > * > * 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/

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