R 中如何得到上一级目录

脱裤子放屁太麻烦 直接用函数dirname即可

qoiqpwqr 发表于 2012-12-16 12:34
这个有点麻烦

如果你原来的的字符串是d:\temp\aaa.jpg，\t和\a会被认为是特殊的字符，比如\t代表tab

传递进去的！

"问题1：如何根据d:\temp\aaa.jpg 得到d:/temp/aaa.jpg  ？"

The path is not in correct form. It should either be "d:\\temp\\aaa.jpg" or "d:/temp/aaa.jpg".
So it is interpreted by R that your path contains "\t" and "\a" rather than a directory slash.

"问题2：如何根据d:/temp/aaa.jpg 得到上一级目录d:/temp/？"

a="d:/temp/aaa.jpg"
regmatches(a, regexpr(".+/",a))

pacifly 发表于 2013-1-4 03:23
"问题1：如何根据d:\temp\aaa.jpg 得到d:/temp/aaa.jpg  ？"
The path is not in correct form. It should either be "d:\\temp\\aaa.jpg" or "d:/temp/aaa.jpg".
So it is interpreted by R that your path contains "\t" and "\a" rather than a directory slash.
"问题2：如何根据d:/temp/aaa.jpg 得到上一级目录d:/temp/？"
a="d:/temp/aaa.jpg"
regmatches(a, regexpr(".+/",a))

如果传递进去就是 d:\temp\aaa.jpg呢？谢谢！

dxystata 发表于 2013-1-4 09:31
如果传递进去就是 d:\temp\aaa.jpg呢？谢谢！

no way to automate this because R can't parse the string correctly in such case. Suppose change your original path to "d:\temp\caa.jpg", this will not be valid in R (you can try print it in R console), because "\c" is not a recognized escape. Your original path was just lucky to go through R because "\t" and "\a" happen to be those recognized ones.