如何在 R 中使用 readLines 删除空白行？答案

【问题标题】：How to delete blank lines with readLines in R?如何在 R 中使用 readLines 删除空白行？
【发布时间】：2012-08-08 13:36:59
【问题描述】：

如果文件中有很多空行，R中如何用readLines删除空行？

我知道我可以使用blank.lines.skip=Tin read.table 删除它，在readLines 怎么样？

另外，如何使用 readLines 删除最后一个 \n？

【问题讨论】：

也许您应该改用scan，它比readLines 提供更好的控制。

标签： r

【解决方案1】：

如何使用选择运算符从 readLines 返回的字符向量中查找非空行？

# character vector mimicking readLine output, lines 2, 4, and 5 are blank
lines <- c("aaa", "", "ccc", "", "")
# [1] "aaa" ""    "ccc" ""    ""

# select lines which are blank
lines[which(lines=="")]
# [1] "" "" ""

# conversely, lines which are not
lines[which(lines!="")]
# [1] "aaa" "ccc"

我在上面使用了假的readLine 数据，但实际上我没有看到 readLines 返回\n 用于空行或最后一行。

【讨论】：

【解决方案2】：

一个可重现的例子：

  Z <- readLines(textConnection("line1 , stuff, other stuff\nline2 ,junk\nline3, a blank two lines follow\n\n\nline6\n"))
>     Z
[1] "line1 , stuff, other stuff"      "line2 ,junk"                     "line3, a blink two lines follow"
[4] ""                                ""                                "line6"                          
[7] ""                               
>     Z1 <- Z[sapply(Z, nchar) > 0] # the zero length lines get removed.
> Z1
[1] "line1 , stuff, other stuff"      "line2 ,junk"                     "line3, a blank two lines follow"
[4] "line6"

@Andrie 建议你这样做：

> Z <- scan(textConnection("line1 , stuff, other stuff\nline2 ,junk\nline3, a blink two lines follow\n\n\nline6\n"), 
            what="", sep="\n",blank.lines.skip=TRUE)
Read 4 items
>     Z
[1] "line1 , stuff, other stuff"      "line2 ,junk"                     "line3, a blink two lines follow"
[4] "line6"

【讨论】：