使用 R 中的列名从 DataFrame 中提取特定列
在本文中,我们将了解如何使用 R 编程语言中的列名从数据框中提取特定列。
在 data.frame() 中,我们必须传递 dataframe_name 后跟 $ 符号后跟列名。将 dataframe_name$ 列名传递给 data.frame() 的原因是,从列中提取数据后,我们必须以行和列格式显示数据。所以我们将 dataframe_name $ 列名传递给 data.frame()。
$运算符的语法
data.frame ( dataframe_name $ column_name )
示例 1:在此示例中,我们刚刚使用 data.frame()函数创建了一个数据框,并传递了 3 个包含一些值的向量。在第二步中,我们在 data.frame() 中使用了 $运算符和数据框名称。将 dataframe_name $ column name 传递到 data.frame() 背后的原因是以数据框格式显示提取的列。
R
# creating a data frame with number ,
# string and binary as column names .
df1=data.frame(number = c(1:3),
string = c("One" , "Two" , "Three") ,
Binary = c(001,010,011))
# passing column name of df1 using
# $ symbol to data.frame() function.
data.frame(df1$number)
R
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some
# values
name = c("Mani sharma" ,
"Devi sri prasad" ,
"Thaman SS")
# passing the vectors to data.frame()
# as parameters .
df1 = data.frame(ranking,name)
# Extracting name column from df1 using
# $ symbol
data.frame(df1$name)
R
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some data
name = c("Trivikram" , "RajaMouli SS" , "Puri Jagannadh")
# passing the vectors to the data.frame()
# function
df1 = data.frame(ranking,name)
# Extracting name column from df1
# using $ symbol and passing it to data.frame()
# as parameter .
data.frame(df1$name)
R
# creating a data frame with number
# string and binary as column names .
df1=data.frame(number=c(1:3),
string=c("One" , "Two" , "Three") ,
Binary=c(001,010,011))
# extracting 1 to 3 rows of string
# and binary columns from df1
df2 = df1[c(1:3),c("string","Binary")]
# And storing the extracted data into df2
print(df2) # printing the df2
R
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with
# some data
name = c("Trivikram" , "RajaMouli SS" , "Puri Jagannadh")
no_of_movies = c(15, 10, 12)
# passing the vectors to the data.frame()
# function
df1 = data.frame(ranking,name,no_of_movies)
# extracting 1,2 rows of ranking and name
# columns from df1
df2 = df1[1:2 , c("ranking","name")]
# And storing the data into a variable df2
print(df2)
R
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some values
name = c("Mani sharma" , "Devi sri prasad" , "Thaman SS")
no_of_movies=c(20, 30, 40)
# passing the vectors to data.frame()
# as parameters .
df1 = data.frame(ranking,name,no_of_movies)
# Extracting all rows of name and
# no_of_movies columns from df1
df2 = df1[, c("name", "no_of_movies")]
# And storint into a variable called df2
print(df2)
输出:
示例 2:在此示例中,我们创建了 2 个名为排名和名称的向量,其中包含一些数据。将 2 个向量作为参数传递给 data.frame()函数并将其分配给一个名为 df1 的变量,最后使用 $运算符提取名称列并将其传递给 data.frame()函数以以数据帧格式显示。
电阻
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some
# values
name = c("Mani sharma" ,
"Devi sri prasad" ,
"Thaman SS")
# passing the vectors to data.frame()
# as parameters .
df1 = data.frame(ranking,name)
# Extracting name column from df1 using
# $ symbol
data.frame(df1$name)
输出:
示例 3:在此示例中,我们创建了 2 个名为排名和名称的向量,其中包含一些数据。将 2 个向量作为参数传递给 data.frame()函数。将 data.frame()函数分配给名为 df1 的变量。使用 $运算符和 dataframe_name 提取列名并将其传递给 data.frame()函数以数据帧格式显示提取的列名。
电阻
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some data
name = c("Trivikram" , "RajaMouli SS" , "Puri Jagannadh")
# passing the vectors to the data.frame()
# function
df1 = data.frame(ranking,name)
# Extracting name column from df1
# using $ symbol and passing it to data.frame()
# as parameter .
data.frame(df1$name)
输出:
从数据框中提取多列
多列提取可以通过索引来完成。
Syntax : variable_name = dataframe_name [ row(s) , column(s) ]
Example 1: a=df[ c(1,2) , c(1,2) ]
Explanation : if we want to extract multiple rows and columns we can use c() with row names and column names as parameters. Here in the above example we have extracted 1,2 rows and 1,2 columns data from a data frame and stored into a variable.
Example 2 : b=df [ c(1,2) , c(“id”,”name”) ]
Explanation : If we want to specify column names we can give column names as parameters in c() function . In the above example we have extracted 1,2 rows of ID and name columns.
示例 1:首先,我们正在创建一个包含一些数据的数据框。使用索引我们提取多列。在上面的示例中,我们从 df1 中提取了名为 number 和字符串 的所有行和 2 列,并存储到另一个变量中。最后,打印df2。
电阻
# creating a data frame with number
# string and binary as column names .
df1=data.frame(number=c(1:3),
string=c("One" , "Two" , "Three") ,
Binary=c(001,010,011))
# extracting 1 to 3 rows of string
# and binary columns from df1
df2 = df1[c(1:3),c("string","Binary")]
# And storing the extracted data into df2
print(df2) # printing the df2
输出:
示例 2:首先,我们正在创建一个包含一些数据的数据框。使用索引我们提取多列。在上面的示例中,我们从 df1 中提取了 1,2 行和 2 列名为排名和名称的内容,并将它们存储到另一个变量中。最后,打印df2。
电阻
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with
# some data
name = c("Trivikram" , "RajaMouli SS" , "Puri Jagannadh")
no_of_movies = c(15, 10, 12)
# passing the vectors to the data.frame()
# function
df1 = data.frame(ranking,name,no_of_movies)
# extracting 1,2 rows of ranking and name
# columns from df1
df2 = df1[1:2 , c("ranking","name")]
# And storing the data into a variable df2
print(df2)
输出:
示例 3:首先,我们使用一些数据创建一个数据框。使用索引我们提取多列。在上面的示例中,我们从 df1 中提取了名为 name 和 no_of_movies 的所有行和 2 列,并存储到另一个变量中。最后,打印df2。
电阻
# creating a vector with some values
ranking = c(1 : 3)
# creating another vector with some values
name = c("Mani sharma" , "Devi sri prasad" , "Thaman SS")
no_of_movies=c(20, 30, 40)
# passing the vectors to data.frame()
# as parameters .
df1 = data.frame(ranking,name,no_of_movies)
# Extracting all rows of name and
# no_of_movies columns from df1
df2 = df1[, c("name", "no_of_movies")]
# And storint into a variable called df2
print(df2)
输出: