Produce a graphic tree diagram showing the structure of an R object - r

Question

In R, str() is handy for showing the structure of an object, such as the list of lists returned by lm() and other modelling functions, but it gives way too much output. I'm looking for some tool to create a simple tree diagram showing only the names of the list elements and their structure.
e.g., for this example,
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
...
I would like to get something like this:
This is similar to what I get from tree for file folders in my file system:
C:\Dropbox\Documents\images>tree
Folder PATH listing
Volume serial number is 2250-8E6F
C:.
+---cartoons
+---chevaliers
+---icons
+---milestones
+---minard
+---minard-besancon
The result could be either in graphic characters, as in tree or an actual graphic as shown above. Is anything like this available?

Answer 1

A simple approach to getting this from the str output would be something like...
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