R 简明教程

R - Vectors

向量是 R 中最基本的数据对象，有六种类型的基本向量，它们是逻辑型，整数型，双精度浮点型，复数型，字符型和原始型。

Vectors are the most basic R data objects and there are six types of atomic vectors. They are logical, integer, double, complex, character and raw.

Vector Creation

Single Element Vector

即使你在 R 中只写一个值，它也会变成长度为 1 的向量，且属于以上其中一种向量类型。

Even when you write just one value in R, it becomes a vector of length 1 and belongs to one of the above vector types.

# Atomic vector of type character.
print("abc");

# Atomic vector of type double.
print(12.5)

# Atomic vector of type integer.
print(63L)

# Atomic vector of type logical.
print(TRUE)

# Atomic vector of type complex.
print(2+3i)

# Atomic vector of type raw.
print(charToRaw('hello'))

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1] "abc"
[1] 12.5
[1] 63
[1] TRUE
[1] 2+3i
[1] 68 65 6c 6c 6f

Multiple Elements Vector

Using colon operator with numeric data

Using colon operator with numeric data

# Creating a sequence from 5 to 13.
v <- 5:13
print(v)

# Creating a sequence from 6.6 to 12.6.
v <- 6.6:12.6
print(v)

# If the final element specified does not belong to the sequence then it is discarded.
v <- 3.8:11.4
print(v)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1]  5  6  7  8  9 10 11 12 13
[1]  6.6  7.6  8.6  9.6 10.6 11.6 12.6
[1]  3.8  4.8  5.8  6.8  7.8  8.8  9.8 10.8

Using sequence (Seq.) operator

Using sequence (Seq.) operator

# Create vector with elements from 5 to 9 incrementing by 0.4.
print(seq(5, 9, by = 0.4))

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1] 5.0 5.4 5.8 6.2 6.6 7.0 7.4 7.8 8.2 8.6 9.0

Using the c() function

Using the c() function

如果其中一个元素为字符，则将非字符值强制转换为字符类型。

The non-character values are coerced to character type if one of the elements is a character.

# The logical and numeric values are converted to characters.
s <- c('apple','red',5,TRUE)
print(s)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1] "apple" "red"   "5"     "TRUE"

Accessing Vector Elements

向量的元素通过索引进行访问。 [ ] brackets 用于索引。索引从位置 1 开始，在索引中给出一个负值则从此结果中删除该元素。 TRUE 、FALSE 或 0 和 1 也可用于索引。

Elements of a Vector are accessed using indexing. The [ ] brackets are used for indexing. Indexing starts with position 1. Giving a negative value in the index drops that element from result.TRUE,* FALSE* or 0 and 1 can also be used for indexing.

# Accessing vector elements using position.
t <- c("Sun","Mon","Tue","Wed","Thurs","Fri","Sat")
u <- t[c(2,3,6)]
print(u)

# Accessing vector elements using logical indexing.
v <- t[c(TRUE,FALSE,FALSE,FALSE,FALSE,TRUE,FALSE)]
print(v)

# Accessing vector elements using negative indexing.
x <- t[c(-2,-5)]
print(x)

# Accessing vector elements using 0/1 indexing.
y <- t[c(0,0,0,0,0,0,1)]
print(y)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1] "Mon" "Tue" "Fri"
[1] "Sun" "Fri"
[1] "Sun" "Tue" "Wed" "Fri" "Sat"
[1] "Sun"

Vector Manipulation

Vector arithmetic

两个长度相同的向量可以通过相加、相减、相乘或相除得到一个向量输出结果。

Two vectors of same length can be added, subtracted, multiplied or divided giving the result as a vector output.

# Create two vectors.
v1 <- c(3,8,4,5,0,11)
v2 <- c(4,11,0,8,1,2)

# Vector addition.
add.result <- v1+v2
print(add.result)

# Vector subtraction.
sub.result <- v1-v2
print(sub.result)

# Vector multiplication.
multi.result <- v1*v2
print(multi.result)

# Vector division.
divi.result <- v1/v2
print(divi.result)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1]  7 19  4 13  1 13
[1] -1 -3  4 -3 -1  9
[1] 12 88  0 40  0 22
[1] 0.7500000 0.7272727       Inf 0.6250000 0.0000000 5.5000000

Vector Element Recycling

如果我们对两个长度不等的向量进行算术运算，则较短向量中的元素会被循环利用以完成运算。

If we apply arithmetic operations to two vectors of unequal length, then the elements of the shorter vector are recycled to complete the operations.

v1 <- c(3,8,4,5,0,11)
v2 <- c(4,11)
# V2 becomes c(4,11,4,11,4,11)

add.result <- v1+v2
print(add.result)

sub.result <- v1-v2
print(sub.result)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1]  7 19  8 16  4 22
[1] -1 -3  0 -6 -4  0

Vector Element Sorting

向量的元素可以使用 sort() 函数进行排序。

Elements in a vector can be sorted using the sort() function.

v <- c(3,8,4,5,0,11, -9, 304)

# Sort the elements of the vector.
sort.result <- sort(v)
print(sort.result)

# Sort the elements in the reverse order.
revsort.result <- sort(v, decreasing = TRUE)
print(revsort.result)

# Sorting character vectors.
v <- c("Red","Blue","yellow","violet")
sort.result <- sort(v)
print(sort.result)

# Sorting character vectors in reverse order.
revsort.result <- sort(v, decreasing = TRUE)
print(revsort.result)

当我们执行上述代码时，会产生以下结果 -

When we execute the above code, it produces the following result −

[1]  -9   0   3   4   5   8  11 304
[1] 304  11   8   5   4   3   0  -9
[1] "Blue"   "Red"    "violet" "yellow"
[1] "yellow" "violet" "Red"    "Blue"