st: re counting missing

["Richard Hiscock" <rhiscock@netspace.net.au>]

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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