Reputation: 185
I have a string variable response
, which contains text as well as categories that have already been coded (categories like "CatPlease", "CatThanks", "ExcuseMe", "Apology", "Mit", etc.).
I would like to erase everything in response
except for these previously coded categories.
For example, I would like response
to change from:
"I Mit understand CatPlease read it again CatThanks"
to:
"Mit CatPlease CatThanks"
This seems like a simple problem, but I can't get my regex code to work perfectly.
The code below attempts to store the categories in a variable cat_only
. It only works if the category appears at the beginning of response
. The local macro, cats
, contains all of the words I would like to preserve in response
:
local cats = "(CatPlease|CatThanks|ExcuseMe|Apology|Mit|IThink|DK|Confused|Offers|CatYG)?"
gen cat_only = strltrim(strtrim(ustrregexs(1)+" "+ustrregexs(2)+" "+ustrregexs(3))) if ustrregexm(response, "`cats'.+?`cats'.+?`cats'")
If I add characters to the beginning of the search pattern in ustrregexm
, however, nothing will be stored in cat_only
:
gen cat_only = strltrim(strtrim(ustrregexs(1)+" "+ustrregexs(2)+" "+ustrregexs(3))) if ustrregexm(response, ".+?`cats'.+?`cats'.+?`cats'")
Is there a way to fix my code to make it work, or should I approach the problem differently?
Upvotes: 1
Views: 1026
Reputation: 425448
Spaces can be handled using regex:
local words = "(?!CatPlease|CatThanks|ExcuseMe|Apology|Mit|IThink|DK|Confused|Offers|CatYG)\b\S+\b"
gen wanted = ustrregexra(response, "`words' | ?`words'", "")
This uses an alternation (a regex OR which is coded |
) to match trailing/leading spaces, with the leading space being optional to handle when the entire input is one of the target words.
Upvotes: 1
Reputation: 3271
* Example generated by -dataex-. To install: ssc install dataex
clear
input str50 response
"I Mit understand CatPlease read it again CatThanks"
end
local regex "(?!CatPlease|CatThanks|ExcuseMe|Apology|Mit|IThink|DK|Confused|Offers|CatYG)\b[^\s]+\b"
gen wanted = strtrim(stritrim(ustrregexra(response, "`regex'", "")))
list
. list
+-------------------------------------------------------------------------------+
| response wanted |
|-------------------------------------------------------------------------------|
1. | I Mit understand CatPlease read it again CatThanks Mit CatPlease CatThanks |
+-------------------------------------------------------------------------------+
Upvotes: 2
Reputation: 37368
I don't regard myself as fluent with Stata's regex functions, but this may be helpful:
. clear
. set obs 1
number of observations (_N) was 0, now 1
. gen test = "I Mit understand CatPlease read it again CatThanks"
. local OK "(CatPlease|CatThanks|ExcuseMe|Apology|Mit|IThink|DK|Confused|Offers|CatYG)"
. ssc install moss
. moss test, match("`OK'") regex
. egen wanted = concat(_match*), p(" ")
. l wanted
+-------------------------+
| wanted |
|-------------------------|
1. | Mit CatPlease CatThanks |
+-------------------------+
Upvotes: 2