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> var1 <- 1:5
> var2 <- (1:5)/10
> var3 <- c(
"R and",
"Data Mining",
"Examples",
"Case",
"Studies")
> df1 <- data.frame(var1,var2,var3)
> names(df1) <- c(
"VariableInt",
"VariableReal",
"VariableChar")
> write.csv(df1,
"d://data//dummmyData.csv",row.names = FALSE)
> df2 <- read.csv(
"d://data//dummmyData.csv")
> print(df2)
VariableInt VariableReal VariableChar
1 1 0.1 R
and
2 2 0.2 Data Mining
3 3 0.3 Examples
4 4 0.4 Case
5 5 0.5 Studies
library(RODBC)
connection <- odbcConnect(dsn=
"servername",uid=
"userid",pwd=
"******")
query <-
"SELECT * FROM lib.table WHERE ..."
myData <- sqlQuery(connection, query, errors = TRUE)
odbcClose(connection)
sqlSave()和sqlUpdate()用于写入或更新一个ODBC数据库表。
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
>
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
>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)
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/
The WriteXLS function from the WriteXLS package (link:
http://cran.r-project.org/web/packages/WriteXLS/index.html
) can write data to Excel.
Alternatively, write.xlsx from the xlsx package (link:
http://cran.r-project.org/web/packages/xlsx/
) will also work.
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)
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()
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.
