R语言 选择数据框的特定列 – select()函数

R语言中的 select() 函数用于选择数据框的某一列是否被选中。

语法： select(x, expr)

参数：

x： 数据框

expr： 选择的条件

例1 :

# R program to select specific columns
  
# Loading library 
library(dplyr)
    
# Create a data frame
d <- data.frame( name = c("Abhi", "Bhavesh", "Chaman", "Dimri"),  
                 age = c(7, 5, 9, 16),  
                 ht = c(46, NA, NA, 69), 
                 school = c("yes", "yes", "no", "no") ) 
    
# startswith() function to print only ht data 
select(d, starts_with("ht")) 
    
# -startswith() function to 
# print everything except ht data 
select(d, -starts_with("ht")) 

输出

  ht
1 46
2 NA
3 NA
4 69
     name age school
1    Abhi   7    yes
2 Bhavesh   5    yes
3  Chaman   9     no
4   Dimri  16     no

例2 :

# R program to select specific columns
  
# Loading library 
library(dplyr)
    
# Create a data frame
d <- data.frame( name = c("Abhi", "Bhavesh", "Chaman", "Dimri"),  
                 age = c(7, 5, 9, 16),  
                 ht = c(46, NA, NA, 69), 
                 school = c("yes", "yes", "no", "no") ) 
    
# Printing column 1 to 2 
select(d, 1:2) 
    
# Printing data of column heading containing 'a' 
select(d, contains("a")) 
    
# Printing data of column heading which matches 'na' 
select(d, matches("na")) 

输出

     name age
1    Abhi   7
2 Bhavesh   5
3  Chaman   9
4   Dimri  16
     name age
1    Abhi   7
2 Bhavesh   5
3  Chaman   9
4   Dimri  16
     name
1    Abhi
2 Bhavesh
3  Chaman
4   Dimri