Question

我想删除此示例文本文件中某些标头之间的所有行。

    fileConn <- file("sample.txt")
    one <- "*Keyword"
    two <- "*Node"
    three <- "$ Node,X,Y,Z"
    four <- "1,639982.78040607,4733827.5104821,0"
    five <- "2,639757.59709573,4733830.43494066,0"
    six <- "3,639738.81268144,4733834.3619618,0"
    seven <- "*End"
    writeLines (c(one, two, three, four, five, six, seven), fileConn)
    close(fileConn)

    sample <- readLines("sample.txt")

我想要做的是删除"*Node"和"*End"之间的所有行/行。由于我要处理的是这些标头之间具有不同行长度的文件，因此删除方法仅需要基于标头。我不知道该怎么做，因为我只删除了以前由行号引用的数据框中的行。有什么线索吗？

预期输出为：

    *Keyword
    *Node
    *End

Answer 1

readLines返回一个向量，而不是数据帧，因此我们可以更简单地创建样本输入：

sample = c("*Keyword",
"*Node",
"$ Node,X,Y,Z",
"1,639982.78040607,4733827.5104821,0",
"2,639757.59709573,4733830.43494066,0",
"3,639738.81268144,4733834.3619618,0",
"*End")

找到开始和结束标头，并使用负索引删除介于两者之间的元素：

node = which(sample == "*Node")
end = which(sample == "*End")

result = sample[-seq(from = node + 1, to = end - 1)]
result
# [1] "*Keyword" "*Node"    "*End"

这假设存在一行*Node和一行*End。它还假定至少有一行要删除。您可能想创建一种更健壮的解决方案，并针对某些特殊情况进行一些处理，例如

delete_between = function(input, start, end) {
  start_index = which(sample == start)
  end_index = which(sample == end) 
  if (length(start_index) == 0 | length(end_index) == 0) {
    warning("No start or end found, returning input as-is")
    return(input)
  }
  if (length(start_index) > 1 | length(end_index) > 1) {
    stop("Multiple starts or ends found.")
  } 
  if (start_index == end_index - 1) {
    return(input)
  }
  return(input[-seq(from = start_index + 1, to = end_index - 1)])
}

删除文件中适合某些标题的所有行？

1 个答案: