st: Re: re counting missing

["Sergiy Radyakin" <Radyakin@aoek.uni-hannover.de>]

Hello Richard,

first thing that comes into my mind (not quite a ready program, but quite 
straightforward):

1. create a small file with a single variable listing all possible class5 
categories
2. -contract- your data to keep only unique ids
3. -cross- the two datasets. This will create all pairwise combinations of 
id and class5
4. -merge- this dataset with the original data by id and class5. you will 
have missings in t and number for some combinations
5. -sort- by id and t.
6. Now go with -by(id)- and -replace- number=0 if t==.
7. Go by(id) again and replace t=t[1]
Be sure not to switch steps 6 and 7
8. -gen- proportion=number/t

You might need to sort your data appropriately before merging if Stata 
complains.

Surely this can be done more efficiently.

Best regards,
  Sergiy




----- Original Message ----- 
From: "Richard Hiscock" <rhiscock@netspace.net.au>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, February 23, 2007 8:03 AM
Subject: st: re counting missing



> In study of swallowing I have  oesophageal pressures measured many times 
> on each patient and within patients these are
> coded into one of 5 contraction types. Subjects may have none up to all of 
> the types of contraction & many or no pressures
> measured for each type.
> I wish to count the number of pressures readings  measured for each type 
> of contraction for each patient.
> I have achieved this by (may be a bit long handed)
> by id class5: gen n =_n
>
> by id class5: gen number =_N
>
> by id: gen t=_N
>
> drop if n < number
>
> gen proportion = number/t
>
> format proportion %9.2f
>
> list id group class5 t n number proportion if id <3
>
>      +--------------------------------------------------------+
>     | id     group           class5    t   number   propor~n |
>     |--------------------------------------------------------|
>  1. |  1    reflux           Normal   20       12       0.60 |
>  2. |  1    reflux      synchronous   20        6       0.30 |
>  3. |  1    reflux   High amplitude   20        2       0.10 |
>  4. |  2    reflux      synchronous   12        3       0.25 |
>  5. |  2    reflux   High amplitude   12        1       0.08 |
>  6. |  2    reflux          Failure   12        8       0.67 |
>
>
> In examining the data I wish to look at the distribution of proportion 
> within each class5 category. To do this I need
>
> to record zero in the proportions for class5 categories that did not occur 
> within a subject. For example for subject id 2
>
> +--------------------------------------------------------+
>     | id     group           class5    t   number   propor~n |
>     |--------------------------------------------------------|
>     |  2    reflux           Normal   12        0       0    |
>     |  2    reflux      synchronous   12        3       0.25 |
>     |  2    reflux   High amplitude   12        1       0.08 |
>     |  2    reflux          Failure   12        8       0.67 |
>     |  2    reflux      Ineffective   12        0       0    |
>
> I am unable to achieve this.
>
> Any help would be greatly appreciated.
>
> Richard Hiscock
>
>
>
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