R Basics - R Graphics - page 3

Solution
The most common way to read in a file is to use comma-separated values (CSV) data:

data <- read.csv( "datafile.csv" )

Discussion
Since data files have many different formats, there are many options for loading them. For ex-
ample, if the data file does nothave headers in the first row:

data <- read.csv( "datafile.csv" , header = FALSE FALSE )

The resulting data frame will have columns named V1 , V2 , and so on, and you will probably want
to rename them manually:

# Manually assign the header names
names(data) <- c( "Column1" , "Column2" , "Column3" )

You can set the delimiter with sep . If it is space-delimited, use sep=" " . If it is tab-delimited,
use \t , as in:

data <- read.csv( "datafile.csv" , sep = "\t" )
By default, strings in the data are treated as factors. Suppose this is your data file, and you read
it in using read.csv() :

"First","Last","Sex","Number"
"Currer","Bell","F",2
"Dr.","Seuss","M",49
"","Student",NA,21

The resulting data frame will store First and Last as factors, though it makes more sense in this
case to treat them as strings (or charactersin R terminology). To differentiate this, set string-
sAsFactors=FALSE . If there are any columns that should be treated as factors, you can then
convert them individually:

data <- read.csv( "datafile.csv" , stringsAsFactors = FALSE FALSE )

# Convert to factor
data$Sex <- factor(data$Sex)

str(data)

'data.frame' : 3 obs. of 4 variables:
$ First : chr "Currer" "Dr." ""
$ Last : chr "Bell" "Seuss" "Student"