R语言数据储存与读取

1 首先用getwd() 获得当前目录，用setwd("C:/data")设定当前目录

2 数据保存

创建数据框d

>d <- data.frame(obs = c(1, 2, 3), treat = c("A", "B", "A"), weight = c(2.3, NA, 9))

2.1 保存为简单文本

Usage
write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ",
eol = "\n", na = "NA", dec = ".", row.names = TRUE,
col.names = TRUE, qmethod = c("escape", "double"),
fileEncoding = "")

>write.table(d, file = "c:/data/foo.txt", row.names = F, quote = F) # 空格分隔

>write.table(d, file = "c:/data/foo.txt", row.names = F, quote = F, sep="\t")  # tab 分隔的文件

2.2 保存为逗号分割文本

>write.csv(d, file = "c:/data/foo.csv", row.names = F, quote = F)

2.3 保存为R格式文件

>save(d, file = "c:/data/foo.Rdata")

2.4 保存工作空间镜像

>save.image( ) = save(list =ls(all=TRUE), file=".RData")

3 数据读取

读取函数主要有：read.table( ), scan( ) ，read.fwf( )，readLines().

3.1 用 read.table( ) 读 "c:\data” 下houses.dat

>options(stringsAsFactors=FALSE)

>setwd("C:/data"); HousePrice <- read.table(file="houses.dat")

如果明确数据第一行做表头，则使用header选项

>HousePrice <- read.table("houses.dat", header=TRUE)

options(stringsAsFactors=FALSE)
Exp <- read.table(file="cer.v05.csv",  header=TRUE,  sep=",", row.names= 1)

read.table( ) 变形有： read.csv( ),read.csv2( ), read.delim( ), read.delim2( ).前两读取逗号分割数据，后两个读取其他分割符数据。

3.2  用scan( ) 比read.table( ) 更灵活。

但要指定 变量类型：如：C:\data\data.dat:

M 65 168

M 70 172

F 54 156

F 58 163

>mydata <- scan("data.dat", what = list("", 0, 0))

>mydata <- scan("data.dat", what = list(Sex="", Weight=0, Height=0))

3.3 用read.fwf( )读取文件中一些固定宽度数据

如：C:\data\data.txt:

A1.501.2

A1.551.3

B1.601.4

>mydata <- read.fwf("data.txt", widths=c(1, 4, 3), col.names=c("X","Y","Z"))

4 excel格式数据读取

4.1 利用剪切板

选择excel数据，再用(CTRL+C)复制。在R中键入命令：

>mydata <- read.delim("clipboard")

4.2 使用程序包 RODBC.

如： c:\data\body.xls

Sex Weight Height

M 65 168

M 70 172

F 54 156

F 58 163

> library(RODBC)

> z <- odbcConnectExcel("c:/data/body.xls")

> foo <- sqlFetch(z, "Sheet1")

> close(z)

To an Excel Spreadsheet 保存为Excel文件：

library(xlsx)    #   注意： 软件包需要安装
write.xlsx(mydata, "c:/mydata.xlsx") #   参考： https://danganothererror.wordpress.com/2012/02/12/write-data-frame-to-excel-file/


注意：

1 writeLines 会在最后一行/或者每行末尾加一个换行符

# fileConn<-file(output_fasta)
# writeLines(mystr, fileConn)
# close(fileConn)

fileConn<-file("output.txt")
writeLines(c("Hello","World"), fileConn)
close(fileConn)

txt <- "Hallo\nWorld"
writeLines(txt, "outfile.txt")

or

txt <- c("Hallo", "World")
writeLines(txt, "outfile.txt")

2 另外一个写文件的方法是sink，不会在行末加换行符

sink(output_fasta)
cat(mystr)
sink()

sink("outfile.txt")
cat("hello")
cat("\n")
cat("world")
sink()

> cat("Hello",file="outfile.txt",sep="\n")
> cat("World",file="outfile.txt",append=TRUE)

file.show("outfile.txt")

line="blah text blah blah etc etc"
write(line,file="myfile",append=TRUE) 

write is a wrapper for cat, which gives further details on the format used.

save for writing any R objects, write.table for data frames, and scan for reading data.

readChar(con, nchars, useBytes = FALSE)

writeChar(object, con, nchars = nchar(object, type = "chars"), eos = "", useBytes = FALSE)

# read
fileName <- 'foo.txt'
oldstring<-readChar(fileName, file.info(fileName)$size)

R语言逐行读取文件(一行一行读取文件)：
con <- file("path_file_name", "r")
lineCnt = 0
while(1){
    oneline = readLines(con, n = 1)
    if(length(oneline) == 0){
        break
    }
    lineCnt = lineCnt+1
}
close(con)

R语言读取文件

con <- file(filename, "r")
genes = readLines(con, n = -1)
close(con)

REF:

http://www.statmethods.net/input/exportingdata.html

http://hi.baidu.com/wuyu466/item/d46edcd96c2838e955347f2c