在 R 中提取单列作为 DataFrame
在本文中,我们将看到如何使用 R 编程语言将单个列提取为 Dataframe。
使用中的数据库:
方法 1:使用列名从 Data Frame 中提取数据
在此方法中,可以使用 $ 使用其名称从数据框中提取特定列。
句法:
dataframe$column_name
返回的列将采用向量的形式,但可以使用 R 语言的 data.frame()函数将其显式转换为数据帧。
例子:
R
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extract Specific columns
# Convert it explicitly to a dataframe
specific_col <- data.frame(gfg.data$ GFG_Name,
gfg.data$ GFG_Sal)
print(specific_col)
R
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extract Single Variable as Data Frame
# Using Square Brackets
gfg.data[1]
gfg.data[2]
R
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extracting 2nd column as a separate
# dataframe
x2 <-as.data.frame(gfg.data[,2])
print(x2)
# Extracting 3rd column as a separate
# dataframe
x3 <-as.data.frame(gfg.data[,3])
print(x3)
R
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extract Single Variable as Data Frame
# Using drop Argument
gfg.data[ , 1, drop = FALSE]
gfg.data[ , 2, drop = FALSE]
输出
方法二:使用方括号从数据框中提取数据
也可以使用方括号将该列提取为数据帧,其中将数据帧中列的索引作为输入。
例子:
电阻
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extract Single Variable as Data Frame
# Using Square Brackets
gfg.data[1]
gfg.data[2]
输出
方法 3:提取单列作为 DataFrame
我们从 R 数据框中提取列作为向量,但有时我们可能需要一列作为数据框。因此,我们可以使用as.data.frame来提取我们想要提取为带有单个方括号的数据框的列。这背后的目的可能是将该列与另一个数据框合并。
例子:
电阻
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extracting 2nd column as a separate
# dataframe
x2 <-as.data.frame(gfg.data[,2])
print(x2)
# Extracting 3rd column as a separate
# dataframe
x3 <-as.data.frame(gfg.data[,3])
print(x3)
输出
方法 4:使用 drop Argument 提取单个变量作为数据帧
如果drop 参数的值为 FALSE,则列不会转换为向量对象。
例子:
电阻
# Create the data frame.
gfg.data <- data.frame(
GFG_Id = c (1:7),
GFG_Name = c("Damon","Joe","Jenna","Ryan",
"Bonnie","Stefan","William"),
GFG_Sal = c(6200,5152,6110,7290,8485,7654,
2341),
Start_date = as.Date(c("2021-01-01", "2016-06-27",
"2014-1-09", "2017-02-14",
"2009-03-26","2019-06-27",
"2020-09-27")),
stringsAsFactors = FALSE)
# Print the data frame.
print(gfg.data)
# Extract Single Variable as Data Frame
# Using drop Argument
gfg.data[ , 1, drop = FALSE]
gfg.data[ , 2, drop = FALSE]
输出