RE: st: RE: puzzling "missing" before and after "gen newvar = mdy(a, b, c)"

[Michael McCulloch <mm@pinest.org>]

Very elegant! However, it misses the "99"'s. Example:

. tostring datedx, replace
        datedx was double now str8
. drop if substr(string(datedx),5,2) == "99" | substr(string(datedx),7,2) 
== "99"
        type mismatch




At 02:25 PM 1/11/2007, you wrote:

> Alternative:
>
> drop if substr(string(datedx),5,2) == "99" | substr(string(datedx),7,2) == 
> "99"
> todate datedx, pattern(yyyymmddd) format(%d) gen(datedx1)
>
> Nick
> n.j.cox@durham.ac.uk
>
> Michael McCulloch
>
> > Thanks Nick; this had just occurred to me.
> > I was able to ferret out where the out-of-range days & months were:
> >
> > BEFORE
> > . tostring datedx, replace
> >          datedx was double now str8
> > . generate str4 dxyr1= substr(datedx,1,4)
> > . generate str2 dxmo1 = substr(datedx,5,6)
> > . generate str2 dxda1 = substr(datedx,7,8)
> > . destring dx*, replace
> >          dxyr1 has all characters numeric; replaced as int
> >          dxmo1 has all characters numeric; replaced as byte
> >          dxda1 has all characters numeric; replaced as byte
> > . gen datedx1 = mdy(dxmo1, dxda1, dxyr1)
> > (667 missing values generated)
> >
> > AFTER
> > . tostring datedx, replace
> >          datedx was double now str8
> > . generate str4 dxyr1= substr(datedx,1,4)
> > . generate str2 dxmo1 = substr(datedx,5,6)
> > . generate str2 dxda1 = substr(datedx,7,8)
> > . destring dx*, replace
> > . drop if dxmo==99
> >          (233 observations deleted)
> > . drop if dxda==99
> >          (434 observations deleted)
> > . gen datedx1 = mdy(dxmo1, dxda1, dxyr1)
> > *** no more missing; thanks for your help!***
>
> > At 02:05 PM 1/11/2007, you wrote:
> > >I am glad you are making progress, but if you have any "99"
> > >for month and day, i.e. missing values encoded as such,
> > >then -todate- has no way to work out the correct values.
> > >So, your dates should still be missing in the same place.
> > >It's just that -todate- doesn't squawk at you about them. At
> > this point,
> > >I am not sure that is a feature.
> > >
> > >Nick
> > >n.j.cox@durham.ac.uk
> > >
> > >Michael McCulloch
> > >
> > > > Thanks Nick; using -todate-, now the missing values are no
> > > > longer generated.
> > > >
> > > > . todate datedx , gen(datedx2) pattern(yyyymmdd)
> > > > . format datedx2 %d
> > > >
> > > > Out of curiosity, I looked back at my previous method, and
> > > > found that there
> > > > were day and month ==99.
> > > >
> > > > . summarize dx??1
> > > >      Variable |       Obs        Mean    Std. Dev.       Min
> > > >       Max
> > > >
> > -------------+--------------------------------------------------------
> > > >         dxyr1 |     26806    1990.195    1.958295       1987
> > > >      1993
> > > >         dxmo1 |     26806    7.269828    9.244575          1
> > > >        99
> > > >         dxda1 |     26806    17.66037    15.60529          1
> > > >        99
> > > >
> > > > >summarize dx??1
> > > > >
> > > > >to see which of the days, months, years variables are
> > > > >out of range.
> > > > >
> > > > >Anyway, why are you doing it this way? Only a few days ago
> > > > >a thread you started thrashed out the fact that -todate- from SSC
> > > > >should be able to do it in one line.
> > > > >
> > > > >todate datedx, pattern(yyyymmdd) format(%d) gen(datedx1)
> > > > >Michael McCulloch
> > > > >
> > > > > > I've converted a string date (yyyymmdd) to Stata
> > format, using:
> > > > > >
> > > > > > . * convert datedx to Stata format
> > > > > > . tostring datedx, replace
> > > > > >          datedx was double now str8
> > > > > > . generate str4 dxyr1= substr(datedx,1,4)
> > > > > > . generate str2 dxmo1 = substr(datedx,5,6)
> > > > > > . generate str2 dxda1 = substr(datedx,7,8)
> > > > > > . destring dx*, replace
> > > > > >          dxyr1 has all characters numeric; replaced as int
> > > > > >          dxmo1 has all characters numeric; replaced as byte
> > > > > >          dxda1 has all characters numeric; replaced as byte
> > > > > > . gen datedx1 = mdy(dxmo1, dxda1, dxyr1)
> > > > > >          (387 missing values generated)
> > > > > > . format datedx1 %d
> > > > > >
> > > > > > However, search for missing values before & after my commands
> > > > > > yields nothing:
> > > > > > . list datedx if missing(datedx) in 1/10
> > > > > >
> > > > > > Where might the missing 387 values have originated?
>
> *
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Best wishes,
Michael


____________________________________

Michael McCulloch
Pine Street Clinic
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