[R] case conversion and/or string comparison
Jan_Svatos@eurotel.cz
Jan_Svatos at eurotel.cz
Fri Nov 16 15:31:02 CET 2001
?toupper
converts lower-case to upper-case.
Jan
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/- Jan Svatos, PhD Sokolovska 855/225 -/
/- Data Analyst, Prague 9 -/
/- Eurotel Praha 190 00 -/
/- jan_svatos at eurotel.cz Czechia -/
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- - - Original message: - - -
From: owner-r-help at stat.math.ethz.ch
Send: 11/16/01 2:53:33 PM
To: <r-help at stat.math.ethz.ch>
Subject: [R] case conversion and/or string comparison
This is no doubt trivial but after searching the help files and the web, I
cannot seem to find it.
1) How do I convert 'hgt' into 'HGT' in R?
2) How should I have used the help facilities to find this?
At the end of the day, all I want to do is case insensitive string
matching... i.e. 'if ("HGT" == 'hgt') print('this should be true')'
I tried using some of the regular expression tools but I had some trouble
interpreting the results:
> grep("HGT", "hgt", ignore.case = T)
[1] 1
> grep("HGT", "tem", ignore.case = T)
numeric(0)
This appears to be what I want. However, putting an 'if' around this
fails for the false case.
> if ( grep("HGT", "tem", ignore.case = T) ) print('hi');
Error in if (grep("HGT", "tem", ignore.case = T)) print("hi") :
argument of if(*) is not interpretable as logical
I suppose that R cannot interpret 'if (numeric(0))'. I would think the
following would work?
> grep("HGT", "hgt", ignore.case = T) == 1
[1] TRUE
> grep("HGT", "tem", ignore.case = T) == 1
logical(0)
Note that the bottom is not 'FALSE'? Why?
> if (grep("HGT", "tem", ignore.case = T) == 1) print('hi');
Error in if (grep("HGT", "tem", ignore.case = T) == 1) print("hi") :
missing value where logical needed
I suppose that R cannot interpret 'if (logical(0))' either?
So my question is: How to I return a logical 'TRUE/FALSE' when
comparing 2 strings? Clearly, I am missing something.
Thanks in advance,
Randall
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