[R] read.csv error: invalid multibyte string

[Dennis Fisher]

R version: 2.13.1
OS X

Colleagues,

I am working with a CSV file; for testing purposes, I created an XLS version of the file.  
When I read these files using read.xls (gdata) or read.csv, I encounter an error:
	Error in type.convert(data[[i]], as.is = as.is[i], dec = dec, na.strings = character(0L)) : 
	  invalid multibyte string at '<b0>C'
The error occurs whether or not I invoke the "as.is" option of read.csv.

The trigger for this error is a "degree C" string (\xb0).  The offending line is:
[1] "\"DD4A14\",\"VITALS\",\"SITE038\",\"038-501\",\"SCREENING\",\"\",\"Temperature\",\"37.8\",\"\xb0C\",\"1005_TS\",\"e2\",\"1005/cla\",\"\",5/25/2011,-1,2,0,0,0,0,0,0,1,7/20/2011 16:48:25,240,1"

I can get around the error by reading the file with readLines, then editing out that character:
	PATH <- textConnection(sub("\xb0", "degrees", readLines(PATH)))
	read.csv(PATH, header=T, as.is=T) 
This alternate approach is successful.  This leads to two questions:

1.  Why can readLines handle that character string whereas read.csv cannot?

2.  Reading the text connection is slow -  it takes ~ 11 seconds to read a file with 11K rows.  I edited the file to replace to offending character with "degree".  read.csv reads the 11K rows of the new file in a fraction of a second. Can someone explain why reading the text connection is so much slower than reading a file?

Dennis

Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-866-PLessThan (1-866-753-7784)
www.PLessThan.com