Question

我有一个文件（Map_1.hdr）从乐器生成，这里是文件：

    ENVI
    description = {ROI id #1}
    samples = 16
    lines   = 4
    bands   = 1025
    data type = 4
    interleave = bip
    wavelength = 
    pixel size = {9.38E-07, 7.5E-07}
    x-start and y-start = {0.027363358, -0.007902135}

我需要从最后两行获取特定数据，这些数据：

pixel_size = c(9.38E-07,7.5E-07)
origin = (0.027363358, -0.007902135)

这是我的（不完整）尝试：

library(R.utils)
rem <- 2
nL <- countLines("Map_1.hdr")
df <- read.csv("Map_1.hdr", header=FALSE, sep=" ", skip=nL-rem, stringsAsFactors = FALSE)

有了这个，我得到了最后两排，但我仍然很远，以清理其余的。有没有其他方法可以得到我想要的东西？

Answer 1

这就是我用过的东西：

 txt <-"   ENVI
    description = {ROI id #1}
    samples = 16
    lines   = 4
    bands   = 1025
    data type = 4
    interleave = bip
    wavelength = 
    pixel size = {9.38E-07, 7.5E-07}
    x-start and y-start = {0.027363358, -0.007902135}"
rem <- 2
nL <- length(readLines(textConnection(txt)))
df <- read.delim(text=gsub(patt = "^.+\\{|\\}", 
                                 # ^^^^^^     removes everything upto last '{' 
                                    #     ^^^ as well as the trailing '}' 
                                    #    ^    the `|` char is regex logical OR
                           repl = "",  # by replacing with length zero character
                             readLines(textConnection(txt))), # input text or file
                    header=FALSE, sep=",",  # left the comma in so it can be 'sep'
                    skip=nL-rem, stringsAsFactors = FALSE)
> df
           V1           V2
1 0.000000938  0.000000750
2 0.027363358 -0.007902135

您可以使用文件名替换readLines(textConnection(txt))的实例，并删除text =参数。（它对构建可工作的，可测试的例子非常有用。）

Answer 2

这可行吗？不确定我是否完全理解你想要的输出：

>attempt <- read.table("~/"Map_1.hdr"",  sep= "=", stringsAsFactors = F)

> tail(attempt,2)$ENVI
[1] " {9.38E-07, 7.5E-07}"         " {0.027363358, -0.007902135}"
> tail(attempt,2)$ENVI[1]
[1] " {9.38E-07, 7.5E-07}"
> tail(attempt,2)$ENVI[2]
[1] " {0.027363358, -0.007902135}"

然后，您可以使用strsplit和gsub从那里获得所需内容？

> strsplit(gsub('[\\{}]', "", tail(attempt,2)$ENVI[1]),",")[[1]][1]
[1] " 9.38E-07"
> strsplit(gsub('[\\{}]', "", tail(attempt,2)$ENVI[1]),",")[[1]][2]
[1] " 7.5E-07"

从R中的txt导入特定数据

2 个答案: