Tips to incread the data reading speed in R

Here are some tips to increase the data reading speed in R:

#The purpose is to compare the processing time when using different options to read in data with read.table

# test to read /data02/temp/temp_hsong/test/hsb12.sas7bdat

#1: without any options 

system.time(read.table("/data02/temp/temp_hsong/test/sasxport.txt", header=T))

#2: By default R will convert character vars into factors wile reading

#suppress R convert character variables into factors by stringsAsFactors=F

system.time(read.table("/data02/temp/temp_hsong/test/sasxport.txt", header=T, stringsAsFactors=F))

#3: if data has no comment sign, then tell R

system.time(read.table("/data02/temp/temp_hsong/test/sasxport.txt", header=T, comment.char=''))

#4: roughly tell R a number slightly greater than the number of records

system.time(read.table("/data02/temp/temp_hsong/test/sasxport.txt", header=T, nrows=8000))

#5: When reading data, it's better tell R the mode of each var by colClasses

system.time(read.table("/data02/temp/temp_hsong/test/sasxport.txt", header=T, sep=',', colClasses=c(rep("numeric",11))))

The processing time is: