R language [import and export of dataset]

Catalog

One 、 Enter data from keyboard

Two 、 Function method read

1. Read data file

 2. Read data from the screen

1.scan

2.readline

3. Read fixed width data file

3、 ... and 、 Read csv file

Four 、 Read the table data file

5、 ... and 、 Read tables from the network or CSV Data files  

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One 、 Enter data from keyboard

mydata <- data.frame(age=numeric(0), gender=character(0),
                     weight=numeric(0))
mydata <- edit(mydata)

After entering our above code , We enter a text editing mode , We can use vim The syntax command of editing text to edit our data  

Two 、 Function method read

1. Read data file

x<-scan(text = "1 2 3")
x

# Enter the file path to read , And store the read data as a vector 
w <- scan("/Users/Documents/R/city.txt")
w

w<-scan("/Users/Documents/R/data/weight.data")
w

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 2. Read data from the screen

1.scan

Read numerical data from the screen , After we input our data , We return twice in a row , You can end the input , Generate a numerical vector .

x<-scan()
x

Read string data from the screen  

y <- scan(what="")

Or use the following method

2.readline

readline It can support reading a line of data input from the keyboard , Press enter to transfer the whole row of data into the variable  

x=readline()

 

3. Read fixed width data file

The first parameter is the full pathname of our file , The width is a vector ,w1 Represents the width of the first variable ,w2 Indicates the width of the second variable , And so on .

mydata <- read.fwf("filename",widths=c(W1,W2,...,Wn))

mydata1 <- read.fwf("/Users/Documents/R/city.txt",widths=c(4))
mydata1

 

mydata<-read.fwf("/Users/Documents/R/data/FixWideData.txt",widths=c(10,10,4,-1,4))

 

  We can also specify col.names Method to specify the name of our index , among -1 Parameter means to ignore the space between two years .（ As we R Language entry blog ,-1 Indicates that a column of data is ignored ）

mydata2<-read.fwf("/Users/Documents/R/data/FixWideData.txt",widths=c(10,10,4,-1,4),col.names=c("Last","First","Born","Died"))

The following image is our data file , We found that although our data is long and short , But it is aligned by spaces , So we can specify the width of the file to read our specific data  

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However, we found that such data files will have the following errors  , This is because we didn't enter at the end of the last line of the data file , Our compiler can't find the sign of our end , Just add a carriage return at the end of the file , It won't be wrong

3、 ... and 、 Read csv file

# Here we will transfer our file path 
mydata0<-read.csv("/Users/Documents/R/city.csv")
mydata0

# When we specify our header by F after , The column names in our original dataset are included in the data , Then a new set of indexes will be automatically generated , As shown in the figure below 
mydata1<-read.csv("/Users/Documents/R/city.csv",header = F)
mydata1

as.is It is to set whether to convert character type into factor type variable  

mydata2 <- read.csv("/Users/Documents/R/data/TableData.txt", as.is=F)
mydata2

mydata2 <- read.csv("/Users/Documents/R/data/TableData.txt", as.is=T)
mydata2

Four 、 Read the table data file

Each row of data is an observation

In each observation , Different variables are separated by a separator , Such as the blank space ,tab, The colon , comma

Each observation contains the same number of variables .

read.table( ).
mydata <- read.table(file, header= logical_value,sep="delimiter", rowname="name"

mydata0 <- read.table("/Users/Documents/R/data/TableData.txt")

 

  Of course, we can also specify our separator

mydata1 <- read.table("/Users/Documents/R/data/CommaData.txt", sep=",")
mydata1

 

Added stringAsFactor=False after , Data frames do not convert character types to factors  

mydata2 <- read.table("/Users/Documents/R/data/TableData.txt",stringsAsFactor=FALSE)
mydata2

When we add parameters header=T in the future , The data in the first row of our original data set will become our index  

mydata3 <- read.table("/Users/Documents/R/data/TableData.txt",header=T,stringsAsFactor=F)
mydata3

5、 ... and 、 Read tables from the network or CSV Data files  

read.csv()

read.table()

scan()

Can get the data of the remote server

mydata0 <- read.csv("http://www.example.com/download/data.csv")
mydata1 <- read.table("ftp://ftp.example.com/download/data.csv")