[R] question regarding gregexpr and read.table

[Eik Vettorazzi]

Hi Jack,
yes there is. see ?read.table for option check.names

and to the 2nd task "." is a special character in regular expressions,
so mask it or don't use regular expressions:

gregexpr("[.]","A.B.C.D") #or
gregexpr(".","A.B.C.D",fixed=T)

cheers.

Am 17.08.2011 15:03, schrieb Jack Luo:
> Hi,
> 
> I have a silly question regarding the usage of two commands: read.table and
> gregexpr：
> For read.table, if I read a matrix and set header = T, I found that all the
> dash ("-") becomes dots (".")
> 
> 
> A = read.table("Matrix.txt", sep = "\t", header = F)
> A[1,1]
> # "A-B-C-D".
> 
> A = read.table("Matrix.txt", sep = "\t", header = T)
> colnames(A)[1]
> # "A.B.C.D"
> 
> Is there a way to use the header = T argument, but still keep the original
> format "A-B-C-D"?
> 
> For gregexpr,
> gregexpr("-","A-B-C-D")[[1]]
> #[1] 2 4 6
> #attr(,"match.length")
> #[1] 1 1 1
> 
> 
> gregexpr(".","A.B.C.D")[[1]]
> [1] 1 2 3 4 5 6 7
> attr(,"match.length")
> [1] 1 1 1 1 1 1 1
> 
> Looks like dots means all the characters. Is there a way that I can extract
> the position of the dots specifically?
> 
> Thanks,
> 
> -Jack
> 
> 	[[alternative HTML version deleted]]
> 
> 
> 
> 
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-- 
Eik Vettorazzi
Institut für Medizinische Biometrie und Epidemiologie
Universitätsklinikum Hamburg-Eppendorf

Martinistr. 52
20246 Hamburg

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