read.table() Issue

 What might cause this?

I restored these two files from last Friday and they are read into R with
no problems. So, I'll make one change at a time and see where things break.
Will post results when I have them.

Rich

 What might cause this?

Must be computers acting like computers. Restored files from backup, made
changes one at a time, and there are no problems reading them into R data
frames. My apologies for taking up space here.

Rich

An unmatched quote can make read.table run very slowly
when there are lots of lines in the file.  E.g.,

z <- rep("A B C", 10^6)
z[2] <- "A \"B C" # unmatched quote on line 2
tf <- tempfile()
cat(file=tf, sep="\n", z)
system.time(z2 <- read.table(tf, skip=2)) # skip bad line

user  system elapsed
  0.860   0.028   0.887

str(z2)

'data.frame':   999998 obs. of  3 variables:
 $ V1: Factor w/ 1 level "A": 1 1 1 1 1 1 1 1 1 1 ...
 $ V2: Factor w/ 1 level "B": 1 1 1 1 1 1 1 1 1 1 ...
 $ V3: Factor w/ 1 level "C": 1 1 1 1 1 1 1 1 1 1 ...

system.time(z1 <- read.table(tf, skip=1))

[ no return for several minutes on a 64-bit Linux machine ]

On smaller files it quickly gives the error "line 1 did not have 4 elements",
along with a warning "incomplete final line found by readTableHeader ...".

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
Of Rich Shepard
Sent: Wednesday, August 01, 2012 10:52 AM
To: r-help at r-project.org
Subject: [R] read.table() Issue

   Yesterday I changed the headers for a couple of columns in data text files
and removed hyphens from within character strings, too. When I tried to
re-read these data sources using read.table() I encountered an issue I've
not before seen. Both files were read almost instantly until yesterday's
wording changes.

   Now both files seem to cause R to hang. Rather than having the prompt
immediately returned nothing happens. In emacs the 'working' symbol appears
but the read.table() function does not complete.

   What might cause this?

Rich

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An unmatched quote can make read.table run very slowly when there are lots
of lines in the file.  E.g.,

Bill,

   Yes. Turns out that there was no closing quote on a changed header. I
found this by an error message on one data file; the other data file didn't
generate an error for me to see.

Thanks very much,

Rich