
Dear all,
 
My question is illustrated by the following example:
 
I have a matrix M:
 
> M<- matrix(c("0","0","1","1","0","1","1","0","0","*","1","1","0","1","*"),nrow=3)
> colnames(M)<- c("2006","2007","2008","2009","2010")
> M
     2006 2007 2008 2009 2010
[1,] "0"  "1"  "1"  "*"  "0" 
[2,] "0"  "0"  "0"  "1"  "1" 
[3,] "1"  "1"  "0"  "1"  "*" 
 
> pattern<- c("0","1")
 
I would like to find, for each row, if it contains exactly the pattern of two character strings, beginning with a "0" and followed by a "1", i.e, exactly "0" "1". If it does, at which year?
E.g. It should return 2006 for row 1, 2008 for row 2 and 2008 for row 3.
 
For as far as I know, the variations of the grep function group cannot search for a pattern that has 2 or more character strings. I could do it with a loop but I seek a more efficient way than a loop. How should I do it? Really appreciated for your help!!!
 
Best regards,
Jing Liu
  		 	   		  
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