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1.R數(shù)據(jù)的保存與加載

可通過save()函數(shù)保存為.Rdata文件，通過load()函數(shù)將數(shù)據(jù)加載到R中。

> a <- 1:10
> save(a,file='d://data//dumData.Rdata')
> rm(a)   #將對象a從R中刪除
> load('d://data//dumData.Rdata')
> print(a)
 [1]  1  2  3  4  5  6  7  8  9 10

下面創(chuàng)建df1的數(shù)據(jù)框，通過函數(shù)write.csv()保存為一個.csv文件，然后通過read.csv()將df1加載到數(shù)據(jù)框df2中。

> 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

RODBC提供了ODBC數(shù)據(jù)庫的連接。

3.1從數(shù)據(jù)庫中讀取數(shù)據(jù)

odbcConnect()建立一個數(shù)據(jù)庫連接，sqlQuery()向數(shù)據(jù)庫發(fā)送一個SQL查詢，odbcClose()關閉數(shù)據(jù)庫連接。

library(RODBC)
connection <- odbcConnect(dsn="servername",uid="userid",pwd="******")
query <- "SELECT * FROM lib.table WHERE ..."
# or read query from file
# query <- readChar("data/myQuery.sql", nchars=99999)
myData <- sqlQuery(connection, query, errors = TRUE)
odbcClose(connection)

3.2從Excel文件中導入與導出數(shù)據(jù)

library("RODBC")
conn<-odbcConnectExcel("D:/data/Amtrak.xls")
Amtrak<-sqlFetch(conn,"Data")
close(conn)