R rev() Function - Reverse a Vector
R Language ExamplesThe R rev() function is used to reverse the order of elements in a vector.
It turns the last element of the vector into the first, and the first into the last.
The syntax of the rev() function is as follows:
rev(x)
Parameter description:
xInput vector.
Example
# Reverse numeric vector
x <- 1:10
print("Original vector:")
print(x)
print("After reversal:")
print(rev(x))
# Reverse character vector
months <- month.abb[1:6] # Abbreviations of the first 6 months
print("First 6 months:")
print(months)
print("Reversed:")
print(rev(months))
x <- 1:10
print("Original vector:")
print(x)
print("After reversal:")
print(rev(x))
# Reverse character vector
months <- month.abb[1:6] # Abbreviations of the first 6 months
print("First 6 months:")
print(months)
print("Reversed:")
print(rev(months))
Executing the above code produces the following output:
[1] "原始向量:" [1] 1 2 3 4 5 6 7 8 9 10 [1] "反转后:" [1] 10 9 8 7 6 5 4 3 2 1 [1] "前 6 个月:" [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" [1] "反转:" [1] "Jun" "May" "Apr" "Mar" "Feb" "Jan"
Combining rev() with cumsum() can achieve different cumulative calculation directions:
Example
x <- c(10, 20, 30, 40, 50)
# Forward cumulative sum
print("Forward cumulative sum:")
print(cumsum(x))
# Reverse cumulative sum (accumulate from the end backwards)
print("Reverse cumulative sum:")
print(rev(cumsum(rev(x))))
# Forward cumulative sum
print("Forward cumulative sum:")
print(cumsum(x))
# Reverse cumulative sum (accumulate from the end backwards)
print("Reverse cumulative sum:")
print(rev(cumsum(rev(x))))
Executing the above code produces the following output:
[1] "正向累加:" [1] 10 30 60 100 150 [1] "反向累加:" [1] 150 140 120 90 50Other Extensions