1.3. Loading a Delimited Text Data File
P
roblem
You want to load data from a delimited text file.
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 example, if the data file does not have headers in the first row:
data <- read.csv("datafile.csv", header=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 characters in R terminology). To differentiate
this, set stringsAsFactors=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)
# Convert to factor
data$Sex <- factor(data$Sex)
str(data)
'data.frame': 3 obs. of 4 variables:
1.3. Loading a Delimited Text Data File | 3
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