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Re: st: string function


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: string function
Date   Wed, 24 Aug 2011 12:37:23 +0100

I just said that they _could_ be written.

At that time, I had forgotten about -egen- solutions for your first
problem in -egenmore- (SSC). Both of those solutions (by Nick Winter
and myself) overlooked what now seems to me a cleaner solution using
-subinstr()- and -length()-. See also

<http://statadaily.wordpress.com/2011/01/20/counting-occurrence-of-strings-within-strings/>

and my Speaking Stata column in SJ 11(1) 2011 for discussion.

I am not aware of coded -egen- solutions for your other problems.

I imagine that they would just be wrappers for those -foreach- loops,
with no gain in efficiency or even comprehensibility.

I'm setting them as an exercise for homework.

Nick

2011/8/24 Grace Jessie <gracejessie@hotmail.com>:
> Nick,
> thank you.
> Counld you please also tell me the -egen- solution for my questions?
>
> Grace
>
> ----------------------------------------
>> Date: Wed, 24 Aug 2011 11:59:19 +0100
>> Subject: Re: st: string function
>> From: njcoxstata@gmail.com
>> To: statalist@hsphsun2.harvard.edu
>>
>> Solutions to all these could be written as -egen- functions or Mata functions.
>>
>> Here I focus on "official Stata only" solutions.
>>
>> First question is discussed in
>>
>> Nicholas J. Cox
>> Stata tip 98: Counting substrings within strings
>> The Stata Journal 11(2): 318-320
>>
>> length("abcdaf") - length(subinstr("abcdaf", "a", "", .))
>>
>> Last two questions
>>
>> any of "a", "b", "c"
>>
>> max(strpos("abcdaf","a"), strpos("abcdaf", "b"), strpos("abcdaf", "c")) > 0
>>
>> all of "a", "b", "c"
>>
>> min(strpos("abcdaf","a"), strpos("abcdaf", "b"), strpos("abcdaf", "c")) > 0
>>
>> If you had a long list of candidates, I would do something like this:
>>
>> gen found = 0
>>
>> qui foreach letter in s o m e t h i n g {
>> replace found = max(found, strpos(strvar, "`letter'") > 0)
>> }
>>
>> where for "max" substitute "min" as needed.
>>
>> The mapping max <-> any, min <-> all is discussed in
>> http://www.stata.com/support/faqs/data/anyall.html
>>
>> Nick
>>
>> 2011/8/24 Grace Jessie <gracejessie@hotmail.com>:
>>
>> > How to count how many times a substring appears in a string?
>> > For example,
>> > function("abcdaf","a")=2
>> >
>> > And, how to check if a string variable has certain substrings?
>> > With regard to this, I want to ask two functions.
>> > For example,
>> > function("abcdaf","a","b","c")
>> > One of what I want to do is to return 1 if a or b or c is included in "abcdaf", ;
>> > the other is to return 1 if a, b and c are included in "abcdaf".
>> > Could anyone tell me the correct functions for thoes above?
>> *
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