R语言 向量

Posted 2021-04-18 方舟编译器开源

向量是最基本的R语言数据对象，有六种类型的原子向量。它们是逻辑，整数，双精度，复杂，字符和原始。

创建向量

单元素向量

即使在R语言中只写入一个值，它也将成为长度为1的向量，并且属于上述向量类型之一。

# 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'))

当我们执行上面的代码，它产生以下结果 -

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

多元素向量

对数值数据使用冒号运算符

# Creating a sequence from 5 to 13.v <- 5:13print(v)
# Creating a sequence from 6.6 to 12.6.v <- 6.6:12.6print(v)
# If the final element specified does not belong to the sequence then it is discarded.v <- 3.8:11.4print(v)

当我们执行上面的代码，它产生以下结果 -

[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

使用sequence (Seq.)序列运算符

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

当我们执行上面的代码，它产生以下结果 -

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

使用C()函数

如果其中一个元素是字符，则非字符值被强制转换为字符类型。

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

当我们执行上面的代码，它产生以下结果 -

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

访问向量元素

使用索引访问向量的元素。[]括号用于建立索引。索引从位置1开始。在索引中给出负值会丢弃来自result.TRUE，FALSE或0和1的元素，也可用于索引。

# 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)

当我们执行上面的代码，它产生以下结果 -

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

向量操作

向量运算

可以添加，减去，相乘或相除两个相同长度的向量，将结果作为向量输出。

# Create two vectors.v1 <- c(3,8,4,5,0,11)v2 <- c(4,11,0,8,1,2)
# Vector addition.add.result <- v1+v2print(add.result)
# Vector substraction.sub.result <- v1-v2print(sub.result)
# Vector multiplication.multi.result <- v1*v2print(multi.result)
# Vector division.divi.result <- v1/v2print(divi.result)

当我们执行上面的代码，它产生以下结果 -

[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

向量元素回收

如果我们对不等长的两个向量应用算术运算，则较短向量的元素被循环以完成操作。

v1 <- c(3,8,4,5,0,11)v2 <- c(4,11)# V2 becomes c(4,11,4,11,4,11)
add.result <- v1+v2print(add.result)
sub.result <- v1-v2print(sub.result)

当我们执行上面的代码，它产生以下结果 -

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

向量元素排序

向量中的元素可以使用sort()函数排序。

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)

当我们执行上面的代码，它产生以下结果 -

[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"