无法根据colnames从CRAN_package_db（）中对data.frame进行子集化

Question

我无法按名称从data.frame对tools::CRAN_package_db()进行子集化：

apkgs <- tools::CRAN_package_db()
apkgs[1, 65] # character vector of length one with an MD5sum

# But these don't work:
apkgs[1, "MD5sum"] # NA
apkgs[1, names(apkgs)[65]] # NA

## But these work, even though they're very similar?
mtcars[1, "mpg"]
mtcars[1, names(mtcars)[1]]

任何想法我做错了什么？

Answer 1

它不起作用，因为两列具有相同的名称（14和65）。

但你可以改用：

apkgs[1, which(names(apkgs) == "MD5sum")]