From suharto_anggono at yahoo.com  Thu Aug  6 06:45:19 2015
From: suharto_anggono at yahoo.com (Suharto Anggono Suharto Anggono)
Date: Wed, 5 Aug 2015 21:45:19 -0700
Subject: [Rd] 'vapply' not returning list element names when returned
	element is a length-1 list
Message-ID: <1438836319.93113.YahooMailBasic@web125102.mail.ne1.yahoo.com>

Quote----------------

> If i have a function that returns a named list with 2 (or more) elements,
> then using 'vapply' retains the names of the elements:
> ....
> But if the function only returns one element, then the name "foo" is lost

vapply _always simplifies_ according to the documentation.

In the first case (function return value contains more than one element, and each ), vapply simplifies to a matrix of two lists (!).  The names "foo" and "hello" have been added to the dimnames so you can tell which is which.

in the second case the function return value is a single list and not a matrix of lists (a simple list is simpler than a matrix of lists). The name of the list ('foo') has nowhere to go; instead, you would be assigning the list to a named variable and you don't need the name 'foo'.

Whether that is inconsistent is something of a matter of perspective. Simplification applied as far as possible will always depend on what simplification is possible for the particular return values, so different return values provide different behaviour.

S Ellison 

--------------------------------------

In the first case, the result is a matrix of mode list, which is a list with "dim" attribute of length 2.

For comparison, 'sapply' retains the name "foo".

> sapply(1:3, function(x) list("foo" = "bar"))
$foo
[1] "bar"

$foo
[1] "bar"

$foo
[1] "bar"



[Rd] 'vapply' not returning list element names when returned element is a length-1 list
Suharto Anggono Suharto Anggono