Question

I am trying to specify colClasses in read.csv in an attempt to speed up the reading of csv file. However, I encounter the following problem:

assuming that i have a file called “t.csv”:

"a","b"
"x","0"

Then, if I run the following in R:

data <- read.csv('t.csv' , stringsAsFactors=FALSE, check.names=FALSE , comment.char='', colClasses= c('character','numeric') )

I got this error:

Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  : 
  scan() expected 'a real', got '"0"'

At first I thought it was the problem with my quote. But using quote='”‘ in read.csv didn’t help.

Answer 1

Your second column is not numeric as it is quoted — that makes it text.

So read it as text, then call as.numeric(...) on the column. Or alter the file.