

-----Messaggio originale-----
Da: mauede@alice.it
Inviato: gio 27/05/2010 16.37
A: r-help@stat.math.ethz.ch
Oggetto: how to extract the 1st field from a vector of strings
 
I have the following vector of strings (shown only the first 3 elements)

> desc[1:3]
[1] "hsa-let-7a MIMAT0000062 Homo sapiens let-7a"      
[2] "hsa-let-7a* MIMAT0004481 Homo sapiens let-7a*"    
[3] "hsa-let-7a-2* MIMAT0010195 Homo sapiens let-7a-2*"
> is.vector(desc)
[1] TRUE
> A <- unlist(strsplit(desc[1:3], "  "))
> A
[1] "hsa-let-7a  MIMAT0000062 Homo sapiens let-7a"      
[2] "hsa-let-7a*  MIMAT0004481 Homo sapiens let-7a*"    
[3] "hsa-let-7a-2*  MIMAT0010195 Homo sapiens let-7a-2*"
> as.vector(A)
[1] "hsa-let-7a  MIMAT0000062 Homo sapiens let-7a"      
[2] "hsa-let-7a*  MIMAT0004481 Homo sapiens let-7a*"    
[3] "hsa-let-7a-2*  MIMAT0010195 Homo sapiens let-7a-2*"
> 
I would like to extract only the first field (of variable length). That is I need a vector containing 
"hsa-let-7a "
"hsa-let-7a*"
"hsa-let-7a-2*"

The operator [[]][] works only on the single vector element. I would like to extract the 1st field 
with one single instruction rather than a loop as traditional programming languages request.

Thank you in advance for you help.
Maura



tutti i telefonini TIM!




tutti i telefonini TIM!


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