选择最后一个孩子的班级 - R 编程语言

有一个小学，每个班级都有许多孩子，现在需要编写一个程序来帮助选择最后一个孩子的班级。具体而言，需要找到所有班级中最后一个孩子的名字，并返回他们所在的班级。如果有多个人都是最后一个孩子，则应该返回他们所在班级的名称。

实现代码

# 创建一个数据框，包含学校名、班级名和学生名
school <- data.frame(
  school_name = rep("Example School", 20), # 一所学校有20个班级
  class_name = paste0("Class ", 1:20) # 班级名称
)
students <- data.frame(
  student_name = c("Alice", "Bob", "Charlie", "David", "Eric", "Frank", "George", "Hannah", "Isabelle", "James", # Class 1
                   "Katie", "Liam", "Michael", "Nancy", "Oliver", "Peter", "Quincy", "Rachel", "Steve", "Tina", # Class 2
                   "Ursula", "Violet", "Wendy", "Xander", "Yvonne", "Zoe", "Anna", "Ben", "Catherine", "David", # Class 3
                   "Emily", "Frank", "Grace", "Henry", "Isabelle", "John", "Katherine", "Leo", "Mia", "Nathan", # Class 4
                   "Oliver", "Penelope", "Quincy", "Rachel", "Sarah", "Thomas", "Ursula", "Victoria", "William", "Xander"), # Class 5
  class_name = rep(paste0("Class ", 1:5), each = 10) # 每个班级有10个学生
)

# 找到每个班级最后一个学生的名字
last_students <- students %>% 
  group_by(class_name) %>% 
  slice_tail(n = 1)

# 返回最后一个孩子所在的班级名称
last_student_classes <- last_students$class_name
class_names <- unique(last_student_classes)
if (length(class_names) == 1) {
  result <- paste("The last student is in", class_names)
} else {
  result <- "The last students are in the following classes:"
  for (i in class_names) {
    result <- paste(result, i)
  }
}

代码解释

首先，我们创建了一个数据框来表示学校的每个班级，其中包含每个班级的名称和学校名称。我们还创建了另一个数据框来表示每个班级的所有学生，并将它们与班级名称相关联。

school <- data.frame(
  school_name = rep("Example School", 20), # 一所学校有20个班级
  class_name = paste0("Class ", 1:20) # 班级名称
)
students <- data.frame(
  student_name = c("Alice", "Bob", "Charlie", "David", "Eric", "Frank", "George", "Hannah", "Isabelle", "James", # Class 1
                   "Katie", "Liam", "Michael", "Nancy", "Oliver", "Peter", "Quincy", "Rachel", "Steve", "Tina", # Class 2
                   "Ursula", "Violet", "Wendy", "Xander", "Yvonne", "Zoe", "Anna", "Ben", "Catherine", "David", # Class 3
                   "Emily", "Frank", "Grace", "Henry", "Isabelle", "John", "Katherine", "Leo", "Mia", "Nathan", # Class 4
                   "Oliver", "Penelope", "Quincy", "Rachel", "Sarah", "Thomas", "Ursula", "Victoria", "William", "Xander"), # Class 5
  class_name = rep(paste0("Class ", 1:5), each = 10) # 每个班级有10个学生
)

接着，我们使用 slice_tail() 函数找到每个班级的最后一个学生。我们对 students 数据框进行分组，按 class_name 列分组，使用 slice_tail() 函数返回每个组的最后一个行。

last_students <- students %>% 
  group_by(class_name) %>% 
  slice_tail(n = 1)

最后，我们检查最后一个孩子所在的班级。如果只有一个班级，我们就返回班级的名称。否则，我们将返回所有含有最后一个孩子的班级的名称。

last_student_classes <- last_students$class_name
class_names <- unique(last_student_classes)
if (length(class_names) == 1) {
  result <- paste("The last student is in", class_names)
} else {
  result <- "The last students are in the following classes:"
  for (i in class_names) {
    result <- paste(result, i)
  }
}

结论

这个程序帮助我们找到了最后一个孩子所在的班级名。我们使用了 dplyr 包中的 group_by() 和 slice_tail() 函数来查找每个班级的最后一个学生。最后，我们通过检查最后一个学生所在的班级来找到最后一个孩子所在的班级。