[R] How to fetch specific part from a number of Text files?

[megh]

Thanks Charles for this reply. I have started according to your suggestion
and hopefully I can do it. In the mean time what I was thinking, instead of
calling my text files by their names, is there any mechanism to call them by
the order they are stored in that directory? Means, suppose, I have total
1000 text files in that directory and therefore I create a vector like
sel.no <- c(1:1000). Next I use the i-th element of the vector "sel.no" to
access the i-th file?

With regards,



Charles C. Berry wrote:
> 
> On Mon, 15 Dec 2008, megh wrote:
> 
>>
>> Hi all,
>>
>> I my c: drive I have possibly 1,000 notepad files, with .txt extension.
>> They
>> are named as the dates on which they were saved i.e. 1st file name is
>> "Volume_4-18-2008", 2nd one is "Volume_4-21-2008", 3rd one
>> "Volume_4-22-2008" and so on............
>>
>> Also, content of each file are in same format like :
>>
>> ******** content of 1st file *************
>> section : 1
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> section : 2
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> section : 3
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> section : 4
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>> -----       ---------      ----------    -----------
>>
>> Here all files have 4-sections, just like shown here but contents within
>> each section (i.e. dashed line here) differs file to file.
>>
>> What I have to do is I have to fetch contents of "section : 2" from each
>> file and then save it to a R-object, matrix of list for further analysis.
>>
>> Can you ppl please tell me how to do that?
> 
> Here is the outline:
> 
>  	*) use list.files() or Sys.glob() to get a list of the files
> 
>  	*) write a function that takes the file name as its arg, uses
>             readLines() to swallow the text and uses grep() to find the
>             'section' lines. Then put the 'dashes' in between two section
>             lines into a separate object (say, dash.lines). Then use
> 
>  		as.matrix( read.table(con <- textConnection( dash.lines ) )
>  		close(con)
> 
>  	  to get the numeric values or maybe
> 
>  		sapply( strsplit(dash.lines, "[ ]+"), as.numeric)
> 
>  	*) debug this on one file
> 
> 
>  	*) use lapply  to step thru the list of file names.
> 
> See
> 
>  	?list.files
>  	?Sys.glob
>  	?readLines
>  	?grep
>  	?textConnection
>  	?strsplit
>  	?sapply
> 
> HTH,
> 
> Chuck
> 
> 
>>
>> Thanks and regards,
>> -- 
>> View this message in context:
>> http://www.nabble.com/How-to-fetch-specific-part-from-a-number-of-Text-files--tp21011017p21011017.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
> 
> Charles C. Berry                            (858) 534-2098
>                                              Dept of Family/Preventive
> Medicine
> E mailto:cberry at tajo.ucsd.edu	            UC San Diego
> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> 

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