生成显示R对象结构的图形树图

Question

在R中，str()对于显示对象的结构非常方便，例如lm()和其他建模函数返回的列表列表，但它提供的输出太多。我正在寻找一些工具来创建一个简单的树形图，只显示列表元素的名称及其结构。

例如，对于这个例子，

data(Prestige, package="car")
out <- lm(prestige ~ income+education+women, data=Prestige)
str(out, max.level=2)
#> List of 12
#>  $ coefficients : Named num [1:4] -6.79433 0.00131 4.18664 -0.00891
#>   ..- attr(*, "names")= chr [1:4] "(Intercept)" "income" "education" "women"
#>  $ residuals    : Named num [1:102] 4.58 -9.39 4.69 4.22 8.15 ...
#>   ..- attr(*, "names")= chr [1:102] "gov.administrators" "general.managers" "accountants" "purchasing.officers" ...
#>  $ effects      : Named num [1:102] -472.99 -123.61 -92.61 -2.3 6.83 ...
#>   ..- attr(*, "names")= chr [1:102] "(Intercept)" "income" "education" "women" ...
#>  $ rank         : int 4
#>  $ fitted.values: Named num [1:102] 64.2 78.5 58.7 52.6 65.3 ...
#>   ..- attr(*, "names")= chr [1:102] "gov.administrators" "general.managers" "accountants" "purchasing.officers" ...
#>  $ assign       : int [1:4] 0 1 2 3
#>  $ qr           :List of 5
#>   ..$ qr   : num [1:102, 1:4] -10.1 0.099 0.099 0.099 0.099 ...
#>   .. ..- attr(*, "dimnames")=List of 2
#>   .. ..- attr(*, "assign")= int [1:4] 0 1 2 3
#>   ..$ qraux: num [1:4] 1.1 1.44 1.06 1.06
#>   ..$ pivot: int [1:4] 1 2 3 4
#>   ..$ tol  : num 1e-07
#>   ..$ rank : int 4
#>   ..- attr(*, "class")= chr "qr"
#>  $ df.residual  : int 98
...

我想得到这样的东西：

这类似于我从tree获取文件系统中文件夹的内容：

C:\Dropbox\Documents\images>tree
Folder PATH listing
Volume serial number is 2250-8E6F
C:.
+---cartoons
+---chevaliers
+---icons
+---milestones
+---minard
    +---minard-besancon

结果可以是图形字符，如tree或实际图形，如上所示。有这样的东西吗？

Answer 1

从str输出中获取此信息的简单方法就是......

a <- capture.output(str(out, max.level=2))
a <- trimws(gsub("\\:.*", "", a[grepl("\\$", a)]))
cat(a, sep="\n")

$ coefficients
$ residuals
$ effects
$ rank
$ fitted.values
$ assign
$ qr
..$ qr
..$ qraux
..$ pivot
..$ tol
..$ rank
$ df.residual
$ xlevels
$ call
$ terms
$ model
..$ prestige
..$ income
..$ education
..$ women