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Re: st: How to keep if freq of var is >= 100 for both group (Alcohol "1" and non-alcohol "0")?
From
Caliph Omar Moumin <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: How to keep if freq of var is >= 100 for both group (Alcohol "1" and non-alcohol "0")?
Date
Tue, 25 Sep 2012 01:28:11 -0700 (PDT)
Thank Nick for your quick reply
I when i apply this command it is keeping if either of the two group is >= 100 observation. Which means there are cases which one of the groups have 0 observations
I would like if and only if both groups have >=100 observations.
Thank you again Nick
Kind Regards,
Caliph
Email: [email protected]
----- Original Message -----
From: Nick Cox <[email protected]>
To: [email protected]
Cc:
Sent: Tuesday, September 25, 2012 9:33 AM
Subject: Re: st: How to keep if freq of var is >= 100 for both group (Alcohol "1" and non-alcohol "0")?
Your title said ">="; your text varies between ">=" and "more than";
clearly you need to choose between ">=" and ">".
On Tue, Sep 25, 2012 at 8:31 AM, Nick Cox <[email protected]> wrote:
> This is a simple application of -by:-, with which all long-term Stata
> users should be familiar.
>
> bysort diagnosis group : keep if _N > 100
>
> Note that this procedure just counts observations, and is indifferent
> to missing values. If you have missing values on key variables, -drop-
> them first.
>
> Read the sections on -by:- in [U}. Then for a discursive tutorial on -by:-, see
>
> 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 Tue, Sep 25, 2012 at 7:53 AM, Caliph Omar Moumin
> <[email protected]> wrote:
>>
>> I have a large dataset which more than 500,000 observations; and more than 7000 diagnoses, which is grouped into two groups alcohol coded as "1" and nonlacloh as "0"
>> the data structure is like this
>>
>> obs id diagnosis group............other variables
>> 1 2338 A120 1
>>
>> 2 3838 m23 0
>> .
>> .
>> .
>> .
>> 500,000 45566 y678 1
>>
>>
>> So i want to keep if observations is >= 100 for both groups alcohol and nonalcohol based on daignoses. For example if daignoses A120 has more than 100 observations for both alcohol and nonalcohol keep if not drop it.
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