R:获取向量中所有元素的索引? [英] R: Get indices of all elements in a vector?

问题描述

简单的问题，但我找不到答案.

Simple questions, but I can't find an answer.

我有一个向量

a<-c(5,6,7)

如何获取向量中所有元素的索引?

how can I get back the indices for all elements in my vector?

我需要回来

1  #"a"
2  #"b"
3  #"c"

或 c(1,2,3)

如果我运行seq_along(a)，它会返回(1,1,1)而不是(1,2,3):

If I run seq_along(a), it gives me back (1,1,1) not (1,2,3):

for (i in seq_along(a)) {
  print(seq_along(a[[i]])) 
}

[1] 1
[1] 1
[1] 1

原因是我需要为每个图创建一个唯一的名称.我有大约100个图，说明了100个位置.位置名称太长且包含特殊字符，因此我无法使用它们来命名输出图.我想使用索引值来代替每个已保存图的名称.

The reason for this is that I need to create a unique name for each of my plots. I have about 100 plots illustrating 100 locations. Locations'names are too long and contain special characters, thus I can't use them to name my output plots. I would like to use the index value to substitute the name for each saved plot.

我需要修改的功能:

lineCumRateGraph <- function(tab, na.rm = TRUE, ...) {

  # Create list of locations
  type_list <-unique(tab$uniqueLoc)

  # Create a for loop to produce ggplot plots
  for (i in seq_along(type_list)) {

    # create a plot for each loc in df
    plot<-

      ggplot(subset(tab, tab$uniqueLoc == type_list[i]),
             aes(x = factor(gridcode), 
                 y = cumRate) +
      geom_line(aes(linetype = distance),
                size = 1) +
      ggtitle(type_list[i])

    windows(width = 4, height = 3.5)
    print(plot)
    ggsave(plot,
           width = 3.5, height = 3.5,
           file = paste(outPath,
                        "lineCumRate",
                       # type_list[i], # I need to replace this one by index value
                        ".png",
                        sep=''),
           dpi = 300)
  }
}

推荐答案

这是 seq_along 函数所服务的目的:

This is the purpose served by the seq_along function:

seq_along(a)
[1] 1 2 3
> cbind( seq_along(a), a)
         a  
[1,] "1" "a"
[2,] "2" "b"
[3,] "3" "c"
>  data.frame( sq = seq_along(a), a)
  sq a
1  1 a
2  2 b
3  3 c

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