R语言 向量
2022-06-16 15:01 更新
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 <- 5:13 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] "Sat"
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+v2 print(add.result) # Vector substraction. 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+v2 print(add.result) sub.result <- v1-v2 print(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"
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