topic Re: reg expressions part II-controlling the "no" in the expression in SAS Procedures

reg expressions part II-controlling the "no" in the expression

LB — Mon, 23 Jul 2012 14:34:05 GMT

Hello all-

I am attempting to use a regular expression such as below:

prxparse('/[ N|N| n|n]o.{1,30}infiltrate/i');

For no infiltrate or No infiltrate.

However it is also picking up non xxx infiltrate, normal...infiltrate.

How do I limit it to just no?

I do need the character spaces as there are quite a number of words that can can appear between the two words.

Thank you.

Lawrence

Re: reg expressions part II-controlling the "no" in the expression

Doc_Duke — Mon, 23 Jul 2012 14:59:09 GMT

Welcome to the world of "natural language processing" (NLP). In specific cases like that I have addressed it with subsequent if-then-else constructs to get at the special cases. You have to do a bit of desk checking and additional review for new special cases when the data are refreshed.

Certainly not ideal, but works OK when the searching is reasonably well contained.

Doc

Re: reg expressions part II-controlling the "no" in the expression

Keith — Mon, 23 Jul 2012 16:08:22 GMT

You can simplify your expression to prxparse('/no\b.*infiltrate/i')

The "\b" defines a word boundary, ".*" then matches any number of characters before "infiltrate". You already have "/i" at the end of the expression to ignore case, therefore you don't need to specify "N|N n|n" etc.

Re: reg expressions part II-controlling the "no" in the expression

LB — Mon, 23 Jul 2012 17:45:27 GMT

Thanks Keith-That helps immensely-One quick question-what if I do want to set the number of characters as

I don't want to see 'no '500 characters' infiltrate' which is entirely possible. That is why I was containing it to 30 characters.

Lawrence

Re: reg expressions part II-controlling the "no" in the expression

Keith — Tue, 24 Jul 2012 07:36:05 GMT

Then just change .* to .{1,30} in the expression, as per your original post. This will allow up to 30 characters between 'no' and 'infiltrate'

Re: reg expressions part II-controlling the "no" in the expression

LB — Mon, 30 Jul 2012 18:20:25 GMT

many thanks Keith!