[R] grep lines before or after pattern matched?

[Simon Kiss]

Hi Josh,
Sorry for the insufficient introduction. This might work, but I'm not sure.
The file that I have includes up to 100 documents (Document 1, Document 2, Document 3....Document 100) with the newspaper name following 4 lines below each Document number.
I'm using readlines to get the text file into R and then trying to use grep to get the newspaper name for each record. But your idea of indexing the text object read into R with the line number where the newspaper name is found is a good one.  I'll just have to come up with a loop to tell R to get the 4th, 8th, 12, 16th, line, etc. 
I'll see if I can get that to work.
Simon
On 2011-07-11, at 12:45 PM, Joshua Wiley wrote:

> Dear Simon,
> 
> Maybe I don't understand properly....if you are doing this in R, can't
> you just pick the line you want?
> 
> Josh
> 
> ## print your data to clipboard
> cat("Document 1 of 100 \n \n \n Newspaper Name \n \n Day Date", file =
> "clipboard")
> ## read data in, and only select the 4th line to pass to grep()
> grep("pattern", x = readLines("clipboard")[4])
> 
> 
> On Mon, Jul 11, 2011 at 9:31 AM, Simon Kiss <sjkiss at gmail.com> wrote:
>> Dear colleagues,
>> I have a series of newspaper articles in a text file, downloaded from a text file.  They look as follows:
>> 
>> Document 1 of 100
>> \n
>> \n
>> \n
>> Newspaper Name
>> \n
>> \n
>> Day Date
>> 
>> I have a series of grep scripts that can extract the date and convert it to a date object, but I can't figure out how to grep the newspaper name.  There is no field ID attached to those lines. The best I can come up with would be to have the program grep the four lines following matching the pattern "Document [0-9]".  There is an an argument to grep in unix that can do this ...grep -A4 'pattern' infile>outfile, but I don't know if there is an equivalent argument in R.
>> 
>> Any thoughts.
>> Yours, Simon Kiss
>> *********************************
>> Simon J. Kiss, PhD
>> Assistant Professor, Wilfrid Laurier University
>> 73 George Street
>> Brantford, Ontario, Canada
>> N3T 2C9
>> Cell: +1 905 746 7606
>> 
>> ______________________________________________
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>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>> 
> 
> 
> 
> -- 
> Joshua Wiley
> Ph.D. Student, Health Psychology
> University of California, Los Angeles
> https://joshuawiley.com/

*********************************
Simon J. Kiss, PhD
Assistant Professor, Wilfrid Laurier University
73 George Street
Brantford, Ontario, Canada
N3T 2C9
Cell: +1 905 746 7606