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POExact string match
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copied!<p>A very trivial question - tried a few iterations and still couldnt get the right answer. Maybe "grep" is not the right command or my understanding is completely off.</p> <p>I have a string: </p> <pre><code>"Part 2.2 are Secondary objectives of this study". </code></pre> <p>I am trying to do an exact match on: "Secondary objective". I thought I could use "fixed=TRUE" here, but it matches both.</p> <pre><code>> str5 = "Part 2.2 are Secondary objectives of this study" > line<-grep("Secondary objectives",str5,fixed=TRUE) > line [1] 1 > str5 = "Part 2.2 are Secondary objectives of this study" > line<-grep("Secondary objective",str5,fixed=TRUE) > line [1] 1 </code></pre> <p>I understand that "grep" is doing exactly as it should. It is searching for the string "Secondary objective" which is technically in the original string. But my understanding is I could do an exact match using the "fixed=TRUE' command. But obviously I am mistaken. </p> <p>If "grep" with "fixed=TRUE" is not the right command for exact match,what will work? "str_match" did not work either. If my pattern is: "Secondary objective", it should return "integer(0)" but if my pattern is "Secondary objectives", it should return 1. </p> <p>Any input is greatly appreciated. Thanks much! - simak</p> <hr> <p>Update: Trying out Arun's suggestion below - works fine as is.</p> <pre><code> str5 = "Part 2.2 are Secondary objectives of this study" > grep("(Secondary objectives)(?![[:alpha:]])",str5, perl=TRUE) [1] 1 > grep("(Secondary objective)(?![[:alpha:]])",str5, perl=TRUE) integer(0) </code></pre> <blockquote> <p>str5 = "Part 2.2 are Secondary objectives of this study" grep("(pat)(?![[:alpha:]])",str5, perl=TRUE) integer(0)</p> </blockquote> <pre><code>However when I did this: > str5 = "Part 2.2 are Secondary objectives of this study" > pat <- "Secondary objectives" > grep("(pat)(?![[:alpha:]])",str5, perl=TRUE) integer(0) Thought I can call "pat" inside "grep". Is that incorrect? Thanks! </code></pre>

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