[R] Exact matching with grep

Vladimir Eremeev wl2776 at gmail.com
Mon Feb 5 15:13:19 CET 2007


Thank you.
There was my misunderstanding of the documentation.
(Un)fortunately, I haven't met the cases, when my code worked incorrectly.


Peter Dalgaard wrote:
> 
> Vladimir Eremeev wrote:
>> Mahieux Dimitri wrote:
>>> I would know if it is possible with grep to match a exact string. For 
>>> example, I want to match the string "DP2" (and only this) and grep match 
>>> "DP2BS" too.
>>> I have sought in the grep help but I didn't find what I want.
>> grep("DP2", {other arguments}, fixed=TRUE)
>>
>> ?grep says that "fixed is logical. If TRUE, pattern is a string to be
>> matched as is. Overrides all conflicting arguments."
>>   
> That's not the issue here:
>> grep("DP2", c("DP2","x", "DP2BS","y"))
> [1] 1 3
>> grep("DP2", c("DP2","x", "DP2BS","y"), fixed=TRUE)
> [1] 1 3
>> grep("^DP2$", c("DP2","x", "DP2BS","y"))
> [1] 1
>> which("DP2"==c("DP2","x", "DP2BS","y"))
> [1] 1
> 
> "fixed=TRUE" avoids special interpretation of metacharacters, but that
> doesn't solve the problem of matching the entire string.
> 

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