[R] extracting information from txt file

[David Winsemius]

On Oct 31, 2012, at 11:11 AM, David Winsemius wrote:

> 
> On Oct 31, 2012, at 9:46 AM, chuck.01 wrote:
> 
>> Hello,
>> 
>> Here is a link to some data:
>> http://www.epa.gov/emap/html/data/surfwatr/data/mastreams/9396/wchem/chmval.txt
>> 
>> I am trying to read this in, and want to use: 
>> chmval <-
>> read.table("http://www.epa.gov/emap/html/data/surfwatr/data/mastreams/9396/wchem/chmval.txt",
>> sep=",", skip= 84, header=T)
>> 
>> the # 84, for 84 lines skipped needs to be derived from the 5th line of the
>> txt file  
>> # Header Records:  85 
>> 
>> so, I need that # (-1) for input into the read.table statement above
> 
> That "# (-1)" is fairly cryptic to my reading, but it appears you are seeing the
> behavior of the "3" character in terminating input for comments.

That would be the shifted-"3".


> Changing the comment character in the call to read.table will allow input from that line.
> 
> ?read.table
> 
> You will need to read only the first 5 or 6 lines first, then execute a separate read.table while skipping input from those lines as well as the variable list that forms a secondary header.
> 
>> headfrm <- read.table( file=url( "http://www.epa.gov/emap/html/data/surfwatr/data/mastreams/9396/wchem/chmval.txt"), nrows=6, sep=":", comment.char="")
>> headfrm
>                V1                                       V2
> 1          Dataset               EMAP Stream Chemistry Data
> 2        File Name                                   chmval
> 3     Date Created                                 02/22/99
> 4      # Variables                                       75
> 5 # Header Records                                       85
> 6   # Data Records                                      711
> 
> 
> 
>> 
>> I've tried grep but that didn't work: 
>> (for this I downloaded the txt file and manually removed that hash mark!)
>> 
>> grep("Header Records:", read.table("chmval.txt", header=T))
>> Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings, 
>> : 
>> line 1 did not have 5 elements
>> 
>> Any ideas?
>> Can I just extract the 5th line?
>> 
>> 
>> 
>> 
>> --
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>> 
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>> and provide commented, minimal, self-contained, reproducible code.
> 
> David Winsemius, MD
> Alameda, CA, USA
> 
> ______________________________________________
> 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.

David Winsemius, MD
Alameda, CA, USA