[R] Exact String Compare in R?

[Gábor Csárdi]

On Tue, Nov 3, 2009 at 2:41 PM, bamsel <benamsel at gmail.com> wrote:
>
> Dear R users:
> Here's a barebones example of what I can't make work.
> As you can see, regexpr() does not perform an exact string match, which only
> occurs in row 1 of these data frames. Instead, as it's supposed to do, it
> finds "b" in "bb" and "c" in "cc". Does anybody know what function I can use
> such that only the first rows would be matched (ie, exact string match?)
> I've also tried simply using the == operator, in which case i get the
> error:"level sets of factors are different"

Because they are not strings, but factors. Convert them to strings
with as.character and use "==".

Best,
Gabor

> Thank you in advance,
> B
>
>> ## two toy data frames, containing character arrays
>> D1=as.data.frame(c("a","b","c"))
>> D2=as.data.frame(c("a","bb","cc"))
>>
>> ## loop through each comparing the strings in each row
>> i=1 #counter
>> while (regexpr(D1[i,1], D2[i,1]) == TRUE) {
> +        cat("identical match on row #", i, "\n")
> +        i=i+1
> +         if (i>3) break
> + }
> identical match on row # 1
> identical match on row # 2
> identical match on row # 3
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>
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-- 
Gabor Csardi <Gabor.Csardi at unil.ch>     UNIL DGM