如何使用数据框中的值作为 R 中的 for 循环迭代器？

Question

我正在尝试将数据帧中的数值设置为 R 中 for 循环中的迭代器条件，但我无法使其工作。

脚本的思路是这样的：

1. 循环遍历数据框中的行
2. 对于每一行，循环一个块的次数与该行中的值所指示的一样多

例如，我有一个名为 events 的数据框，如下所示：

Row     Event        Years
 1        1           10
 2        2           7

我想运行以下循环来执行上面的脚本：

for (i in 1:nrow(events)){
  for(j in 1:events[i,2]{
    print(paste('The event number is',i,'and the year number is',j))
  }
}

我正在寻找的结果如下所示：

[1] "The event number is 1 and the year number is 1."
[1] "The event number is 1 and the year number is 2."
[1] "The event number is 1 and the year number is 3."
[1] "The event number is 1 and the year number is 4."
[1] "The event number is 1 and the year number is 5."
[1] "The event number is 1 and the year number is 6."
[1] "The event number is 1 and the year number is 7."
[1] "The event number is 1 and the year number is 8."
[1] "The event number is 1 and the year number is 9."
[1] "The event number is 1 and the year number is 10."
[1] "The event number is 2 and the year number is 1."
[1] "The event number is 2 and the year number is 2."
[1] "The event number is 2 and the year number is 4."
[1] "The event number is 2 and the year number is 5."
[1] "The event number is 2 and the year number is 6."
[1] "The event number is 2 and the year number is 7."

但我得到的结果是：

[1] "The event number is 1 and the year number is 1."
[1] "The event number is 2 and the year number is 1."
[1] "The event number is 2 and the year number is 2."

出于测试目的，我尝试了以下代码，它按照我想要的方式工作......

for (i in 1:nrow(events)){
  for(j in 1:10){
    print(paste('The event number is',i,'and the year number is',j))
  }
}

...所以我已经尝试了所有可以动态复制10 值的方法。

我是 R 新手，但我对编程并不陌生；从如何调用索引到值的类型，再到使用dim() 设置和获取维度，以及下面列出的其他方法，我已经尝试了所有方法：

1. 1:as.numeric(events[i,2]
2. 1:events$Years[i]
3. 1:as.integer(events[i,2])
4. 1:as.factor(events[i,2])

我认为我将迭代器视为单个值（如整数），而不是像因子或向量这样的 R 构造，这就是我遗漏的地方。我还阅读了有关使用apply 函数解决此类问题的信息，但我不熟悉它的用法，所以我想先尝试解决for 循环。

有人知道我这里有什么问题吗？为此，我整天都在拔头发！

提前感谢您的帮助。

Answer 1

试试：

df <- read.table(header = TRUE, text = "Row     Event        Years
1        1           10
2        2           7")

Count <- do.call("c", lapply(df$Years, function(x) seq(1, x)))
df <- df[rep(df$Event, df$Years) ,]
df <- cbind(df, Count)

paste("The event number is", df$Event, "and the year number is", df$Count)

如果可以矢量化，我认为 for 循环不是一个好主意。