list substring

hi
I ve a list of item x = ( "xxxxx1"
                               "xxxxx2"
                               "yyyyx3")

I need to extract a new vector y  = ( "xxxx",
                                                   "xxxx",
                                                   "yyyy"
)
I mean, for each item I need to extract the first 4 digit
How is that possible?

Thank you
                             

hi
I ve a list of item x = ( "xxxxx1"
                               "xxxxx2"
                               "yyyyx3")

I need to extract a new vector y  = ( "xxxx",
                                                   "xxxx",
                                                   "yyyy"
)
I mean, for each item I need to extract the first 4 digit
How is that possible?
  

calpeda wrote:

hi
I ve a list of item x = ( "xxxxx1"
                               "xxxxx2"
                               "yyyyx3")

I need to extract a new vector y  = ( "xxxx",
                                                   "xxxx",
                                                   "yyyy"
)
I mean, for each item I need to extract the first 4 digit
How is that possible?
  

    sub('^(\\d{4}).*', '\\1', x, perl=TRUE)

vQ

thank you,
but I m importing data from a txt file and I have a matrix of n*1
The function str seems to work only from 1*n

  

calpeda wrote:

thank you,
but I m importing data from a txt file and I have a matrix of n*1
The function str seems to work only from 1*n

  

you see, it would help if you provided more details from the start.  you
may still need to do it;  it seems that both solutions you were given
(mine and the substr one) work for both n*1 and 1*n matrices:

    # 5*1
    (strings = matrix(as.character(sample(10^6, 5)), ncol=1))
   
    substr(strings, 1, 4)
    substr(t(strings), 1, 4)

with a fixed pattern of four digits from the beginning of the string,
the substr solution is better -- simpler and a few times faster.

vQ