r中将数据框中数据类型转化

Before we delve deeper into R programming, it is important to understand the various data types used in R. R has the following basic data types:

在深入研究R编程之前 ，了解R中使用的各种数据类型很重要。R具有以下基本数据类型：

• Character字符
• Numeric数字
• Integer整数
• Logical逻辑上
• Complex复杂

Apart from these basic types, R also supports several data structures that are constructed from the basic types. These are:

除了这些基本类型，R还支持从基本类型构造的几种数据结构。 这些是：

• Vectors向量
• Matrices矩阵
• Arrays数组
• Dataframes数据框
• Lists清单
• Factors因素

This tutorial will help you understand the basic data types. The working of each complex data structure will be covered in more elaborate tutorials.

本教程将帮助您了解基本数据类型。 每个复杂数据结构的工作都将在更详尽的教程中介绍。

R中的数值数据类型 (Numeric Data Types in R)

Since R is predominantly a language designed for statistical purpose, numeric and integer data types are widely used. We will begin with the most frequently used numeric data type. As the name indicates, numeric corresponds to any numerical value. These values can be floating-point, decimal or double.

由于R主要是为统计目的而设计的语言，因此广泛使用数字和整数数据类型。 我们将从最常用的数字数据类型开始。 顾名思义，数值对应于任何数值。 这些值可以是浮点数，十进制数或双精度数。

Before we assign our first variable, please note that the assignment operator in R is <- . Less than symbol followed by a hyphen.

在分配第一个变量之前，请注意，R中的赋值运算符为<- 。 小于符号，后跟连字符。

Begin by assigning random numeric values to variables a, b, and c. The typeof() function in R gives how the variable is stored internally, whereas the class() function tells us what data type class this variable belongs to. R also offers some checking functions starting with “is“. The function is.numeric() when called upon a variable returns a Boolean value of whether the object is of the numeric data type. There are respective is functions for other classes as well.

首先为变量a，b和c分配随机数值。 R中的typeof()函数给出了变量在内部的存储方式，而class()函数则告诉我们该变量属于哪种数据类型。 R还提供了一些以“ is ”开头的检查功能。 调用变量时，函数is.numeric()返回布尔值，该布尔值表示对象是否为数字数据类型。 其他类别也有各自的功能。

Run the following code in your script editor. Place the cursor on the first line and execute each line pressing Ctrl+ Enter. Also observe how these variables start to become a part of your environment window as you run each line.

在脚本编辑器中运行以下代码。 将光标放在第一行上，然后按Ctrl + Enter执行每一行。 还要观察在运行每一行时这些变量如何开始成为环境窗口的一部分。

a <- 3
b <- 5.4
c <- -9.5
typeof(a)
typeof(b)
typeof(c)
is.integer(a)
is.numeric(b)
is.numeric(c)
class(a)

Output:

输出：

> a <- 3
> b <- 5.4
> c <- -9.5
> typeof(a)
[1] "double"
> typeof(b)
[1] "double"
> typeof(c)
[1] "double"
> is.integer(a)
[1] FALSE
> is.numeric(b)
[1] TRUE
> is.numeric(c)
[1] TRUE
> class(a)
[1] "numeric"

Note how all the variables are stored as double in the internal storage, irrespective of being defined with floating-point or not, as shown by the typeof() function. The variable a with value 3 is stored as 3.0, a double value. The function call is.integer() returns a FALSE Boolean value because of this. The class(a) line gives our variable’s type numeric.

请注意，如何将所有变量都以双精度形式存储在内部存储中，而不管是否用浮点定义，如typeof（）函数所示。 值为3的变量a被存储为3.0，即双精度值。 因此，函数调用is.integer（）返回FALSE布尔值。 class(a)行提供了变量的类型numeric 。

R中的数据类型 (Data Types in R)

整数 (Integer)

Without any specification a numerical value is treated as a numeric data type by R compiler. Therefore, to define an integer variable, it is necessary to specify so. This is done by using the as.integer() function.

在没有任何说明的情况下，R编译器会将数值视为数字数据类型。 因此，要定义一个整数变量，必须指定它。 这可以通过使用as.integer()函数来完成。

a<-as.integer(a)
typeof(a)
is.integer(a)
is.numeric(a)

Soon after you run the first line of the code, you see the value assigned to a become 3L, as opposed to 3. The suffix L signifies a long integer of range -2*10ˆ9 to +2*10ˆ9. The variable a is both an integer and a numeric, since all integers are numerics, but not vice versa.

运行代码的第一行后不久，您会看到分配给a的值变成3L，而不是3。后缀L表示范围为-2 * 10ˆ9到+ 2 * 10ˆ9的长整数。 变量a既是整数又是数字，因为所有整数都是数字，但反之亦然。

Output:

输出：

> a<-as.integer(a)
> typeof(a)
[1] "integer"
> is.integer(a)
[1] TRUE
> is.numeric(a)
[1] TRUE

字符 (Character)

The character data type in R is meant to be used for both strings and single characters. A character can be simply specified by using a single or double quotes pair as below.

R中的字符数据类型旨在用于字符串和单个字符。 可以通过使用单引号或双引号对来简单地指定字符，如下所示。

name="journaldev"
typeof(name)
name2='journaldev2'
typeof(name2)

Output:

输出：

> name="journaldev"
> typeof(name)
[1] "character"
> name2='journaldev2'
> typeof(name2)
[1] "character"

An integer or a numeric type can be converted into a character using as.character() function.

可以使用as.character（）函数将整数或数字类型转换为字符。

average=0.558
typeof(average)
average=as.character(average)
typeof(average)

Output:

输出：

> average=0.558
> typeof(average)
[1] "double"
> average=as.character(average)
> typeof(average)
[1] "character"

逻辑上 (Logical )

Logical is the data type used to store Boolean values TRUE and FALSE that arise as a result of logical operations. We have already encountered the TRUE and FALSE outputs above as we called the is.numeric() and is.integer() functions above. Let us verify this using the following statement.

逻辑是用于存储由于逻辑运算而产生的布尔值TRUE和FALSE的数据类型。 我们在上面调用了is.numeric()和is.integer()函数时，已经在上面遇到了TRUE和FALSE输出。 让我们使用以下语句对此进行验证。

typeof(is.integer(average))

Output:

输出：

> typeof(is.integer(average))
[1] "logical"

Similarly, variables of logical type can be used to work with all logical operations.

同样，逻辑类型的变量可用于所有逻辑运算。

x=TRUE; y=FALSE
x&y #Logical AND
x|y #Logical OR
!x #Logical NOT
!y #Logical NOT

Output:

输出：

> x=TRUE; y=FALSE
> x&y
[1] FALSE
> x|y
[1] TRUE
> !x
[1] FALSE
> !y
[1] TRUE

复杂 (Complex)

The final basic data type we discuss here is the complex type. This is used to represent complex numbers in mathematics. Complex numbers are of the form a+bi where a and b are integers.

我们在这里讨论的最终基本数据类型是复杂类型。 这用于表示数学中的复数。 复数采用a+bi的形式，其中a和b是整数。

complex=4+2i
typeof(complex)

Output:

输出：

> complex=4+2i
> typeof(complex)
[1] "complex"

If we wish to calculate the square root of -1, which is mathematically known as i, the imaginary component of the imaginary number, We cannot calculate it by using normal sqrt (square root) function.

如果我们想计算-1的平方根，这在数学上称为i ，就是虚数的虚数分量，那么我们就不能通过使用普通的sqrt （平方根）函数来计算它。

typeof(sqrt(-1)) #Throws a warning message.

Output:

输出：

Warning message:
In sqrt(-1) : NaNs produced

This is possible by defining -1 as a complex number first.

通过首先将-1定义为复数，这是可能的。

sqrt(-1+0i)
typeof(sqrt(-1+0i))

Output:

输出：

> sqrt(-1+0i)
[1] 0+1i
> typeof(sqrt(-1+0i))
[1] "complex"

This ends our discussion of the basic data types in R.

至此，我们对R中基本数据类型的讨论结束了。

翻译自: https://www.journaldev.com/34377/data-types-in-r

r中将数据框中数据类型转化