RE: st: differentiating between groups of records with same date

[Tim Evans <Tim.Evans@wmciu.nhs.uk>]

Nick,

Thanks for this. I don't think I want to go with  -distinct- and -unique- as I want a flag variable permanently in the dataset. I've worked through the examples in http://www.stata.com/support/faqs/data-management/number-of-distinct-observations/, I'm not sure I'm translating this very well to my scenario, but that's probably my fault in how I'm thinking about it. So I'll give it some space before looking at it again. 

Best wishes

Tim


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: 31 July 2012 15:30
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: differentiating between groups of records with same date

See

FAQ     . . . . . . . . . . . . . . . . . . .  Number of distinct observations
        . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox and G. Longton
        10/08   How do I compute the number of distinct observations?
                http://www.stata.com/support/faqs/data-management/
                number-of-distinct-observations/


SJ-12-2 dm0042_1  . . . . . . . . . . . . . . . . Software update for distinct
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q2/12   SJ 12(2):352
        options added to restrict output to variables with a minimum
        or maximum of distinct values

SJ-8-4  dm0042  . . . . . . . . . . . .  Speaking Stata: Distinct observations
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q4/08   SJ 8(4):557--568
        shows how to answer questions about distinct observations
        from first principles; provides a convenience command

On Tue, Jul 31, 2012 at 8:27 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:
> Nick,
>
> Apologies for the lack of clarity.
>
> For the following dataset (below) I wish to count the distinct number of proc_type for each patient on a given surgery_date.
>
> patient_no      cancer_no       diag_date       surgery_date      proc_type
>> 9512834         0484360     21may1994       21may1994                 H1
>> 9512834         0484358    21may1994       21may1994                  H2
>> 9512834         0483234    26apr2000       21may2000                  H1
>> 9512834         0483233    26apr2000
>> 0000012         0000012          21Jan1999        21Jan1999           H3
>> 0000012         0000013          21Jan1999        21Jan1999           H3
>> 0000012         0000014          21Jan1999        21Jan1999           H3
>
>
> In my snapshot above, patient_no 000012 has 3 cancers, with a surgery_date of 21Jan1999, but only one proc_type - so my count should be 1. In contrast, patient_number 9512834 has 2 cancers with a surgery_date of 21may1994, and has 2 proc_types on 21may1994 - my count should therefore be 2.
>
> Or put another way, for each surgery date, how many unique proc_types did each patient have.
>
> Hope this is clearer.
>
> Best wishes
>
> Tim
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
> Sent: 31 July 2012 14:02
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: differentiating between groups of records with same date
>
> Sorry, but what's your question?
>
> On 31 Jul 2012, at 13:32, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:
>
>> Hi Nick,
>>
>> I've been taking a look at the reference you pointed me to, and been
>> experimenting, to see how I would count for each patient, the number
>> of different procedures that took place on the same date.
>>
>> Again I have
>>
>> patient_no      cancer_no       diag_date       surgery_date
>> proc_type
>> 9512834         0484360     21may1994       21may1994    H1
>> 9512834         0484358    21may1994       21may1994    H2
>> 9512834         0483234    26apr2000       21may2000    H1
>> 9512834         0483233    26apr2000
>> 0000012         0000012          21Jan1999        21Jan1999    H3
>> 0000012         0000013          21Jan1999        21Jan1999    H3
>> 0000012         0000014          21Jan1999        21Jan1999    H3
>>
>> So I want to say that patient 9512834 had 2 different proc_types on
>> 21may1994 and that patient 0000012 had one operation.
>>
>> Best wishes
>>
>> Tim
>>
>>
>> -----Original Message-----
>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
>> statalist@hsphsun2.harvard.edu] On Behalf Of Tim Evans
>> Sent: 31 July 2012 10:53
>> To: 'statalist@hsphsun2.harvard.edu'
>> Subject: RE: st: differentiating between groups of records with same
>> date
>>
>> Nick,
>>
>> Thanks for this, a handy piece of code/functionality.
>>
>> Best wishes
>> Tim
>>
>>
>> -----Original Message-----
>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
>> statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
>> Sent: 30 July 2012 17:50
>> To: statalist@hsphsun2.harvard.edu
>> Subject: Re: st: differentiating between groups of records with same
>> date
>>
>> bysort patient_no diag_date: gen freq = _N
>>
>> See also
>>
>> SJ-2-1  pr0004  . . . . . . . . . . Speaking Stata:  How to move
>> step by: step
>>        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
>> N. J. Cox
>>        Q1/02   SJ 2(1):86--102                                  (no
>> commands)
>>        explains the use of the by varlist : construct to tackle
>>        a variety of problems with group structure, ranging from
>>        simple calculations for each of several groups to more
>>        advanced manipulations that use the built-in _n and _N
>>
>>
>> Nick
>>
>> On Mon, Jul 30, 2012 at 10:20 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk>
>> wrote:
>>> Hi all,
>>>
>>> I have a group of patients who are in a dataset of cancers. Each
>>> patient may have more than one cancer diagnosed, and so may be
>>> present in my dataset a number of times. Each patient has a unique
>>> patient identifier, and each cancer has a unique cancer identifier.
>>> Each row of data is cancer specific, but does contain the patient
>>> identifier. It is possible that a patient has 2 cancers diagnosed
>>> on the same day in my dataset. What I would like to do is generate
>>> a flag next to each record to show against each cancer the number
>>> of cancers diagnosed on the same day.
>>>
>>> My data are like this:
>>>
>>> patient_no              cancer_no       diag_date       surgery_date
>>> 9512834         0484360 21may1994       21may1994
>>> 9512834         0484358 21may1994       21may1994
>>> 9512834         0483234 26apr2000       21may2000
>>> 9512834         0483233 26apr2000
>>> 0000057         0000057 19jul2009       19jul2009
>>> 0000060         0000060 02nov2009       24nov2009
>>> 0000074         0000074 21sep2009       22nov2009
>>>
>>>
>>> For example, patient 9512834 had 2 cancers diagnosed on 21may1994
>>> and so for cancer_no 0484360 and 0484358, I would like to generate
>>> a new variable with the value 2 against each record. Similiarly
>>> patient 0000057 has only one cancer diagnosed, and so the new
>>> variable would contain 1.

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