R help - Oct 2022 - When using require(), why do I get the error message "Error in if (!loaded) { : the condition has length > 1" ?

# Below, when using require(), why do I get the error message "Error
in if (!loaded) { : the condition has length > 1" ?

# This is my reproducible code:

#create a vector with the names of the packages I want to use
packages_i_want_to_use <- c('base',
'this_pac_does_not_exist')

# Here I get error messages:
require( packages_i_want_to_use[1] )
#Error in if (!loaded) { : the condition has length > 1

require( packages_i_want_to_use[2] )
#Error in if (!loaded) { : the condition has length > 1

# Here I get what I expect:
require('base')

require('this_pac_does_not_exist')
#Loading required package: this_pac_does_not_exist
#Warning message:
#In library(package, lib.loc = lib.loc, character.only = TRUE,
logical.return = TRUE,  :
#  there is no package called ?this_pac_does_not_exist?

require(), similarly to library(), does not evaluate its first argument
UNLESS you add character.only = TRUE

require( packages_i_want_to_use[1], character.only = TRUE)


On Mon, Oct 24, 2022, 12:26 Kelly Thompson <kt1572757 at gmail.com> wrote:
> # Below, when using require(), why do I get the error message "Error
> in if (!loaded) { : the condition has length > 1" ?
>
> # This is my reproducible code:
>
> #create a vector with the names of the packages I want to use
> packages_i_want_to_use <- c('base',
'this_pac_does_not_exist')
>
> # Here I get error messages:
> require( packages_i_want_to_use[1] )
> #Error in if (!loaded) { : the condition has length > 1
>
> require( packages_i_want_to_use[2] )
> #Error in if (!loaded) { : the condition has length > 1
>
> # Here I get what I expect:
> require('base')
>
> require('this_pac_does_not_exist')
> #Loading required package: this_pac_does_not_exist
> #Warning message:
> #In library(package, lib.loc = lib.loc, character.only = TRUE,
> logical.return = TRUE,  :
> #  there is no package called ?this_pac_does_not_exist?
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

? Mon, 24 Oct 2022 12:07:44 -0400
Kelly Thompson <kt1572757 at gmail.com> ?????:
> require( packages_i_want_to_use[1] )
> #Error in if (!loaded) { : the condition has length > 1
This seems to be a bug in require(). In addition to understanding
character strings as arguments, require() can load packages named by
unquoted barewords:

require(base)

This uses non-standard evaluation, and the part that transforms an
unquoted symbol into a package name doesn't expect to see what is
effectively `[`(packages_i_want_to_use, 1) instead of a single symbol.

If you pass the character.only = TRUE argument to require(), this
additional handling is disabled, making your examples work again. It's
a good idea to always pass this argument when calling require() with a
variable as the first argument.

-- 
Best regards,
Ivan

You need to pass character.only = TRUE to require() whenever you
specify the package using a character variable.

I agree, the error message is confusing.

/Henrik

On Mon, Oct 24, 2022 at 9:26 AM Kelly Thompson <kt1572757 at gmail.com>
wrote:
>
> # Below, when using require(), why do I get the error message "Error
> in if (!loaded) { : the condition has length > 1" ?
>
> # This is my reproducible code:
>
> #create a vector with the names of the packages I want to use
> packages_i_want_to_use <- c('base',
'this_pac_does_not_exist')
>
> # Here I get error messages:
> require( packages_i_want_to_use[1] )
> #Error in if (!loaded) { : the condition has length > 1
>
> require( packages_i_want_to_use[2] )
> #Error in if (!loaded) { : the condition has length > 1
>
> # Here I get what I expect:
> require('base')
>
> require('this_pac_does_not_exist')
> #Loading required package: this_pac_does_not_exist
> #Warning message:
> #In library(package, lib.loc = lib.loc, character.only = TRUE,
> logical.return = TRUE,  :
> #  there is no package called ?this_pac_does_not_exist?
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Reread ?require more carefully. Especially for the  'package' argument.

Incidentally, you don't need to require base. It's always available.

-- Bert

On Mon, Oct 24, 2022 at 9:25 AM Kelly Thompson <kt1572757 at gmail.com>
wrote:
>
> # Below, when using require(), why do I get the error message "Error
> in if (!loaded) { : the condition has length > 1" ?
>
> # This is my reproducible code:
>
> #create a vector with the names of the packages I want to use
> packages_i_want_to_use <- c('base',
'this_pac_does_not_exist')
>
> # Here I get error messages:
> require( packages_i_want_to_use[1] )
> #Error in if (!loaded) { : the condition has length > 1
>
> require( packages_i_want_to_use[2] )
> #Error in if (!loaded) { : the condition has length > 1
>
> # Here I get what I expect:
> require('base')
>
> require('this_pac_does_not_exist')
> #Loading required package: this_pac_does_not_exist
> #Warning message:
> #In library(package, lib.loc = lib.loc, character.only = TRUE,
> logical.return = TRUE,  :
> #  there is no package called ?this_pac_does_not_exist?
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Don't load base. It is already loaded.

On October 24, 2022 9:07:44 AM PDT, Kelly Thompson <kt1572757 at
gmail.com> wrote:
># Below, when using require(), why do I get the error message "Error
>in if (!loaded) { : the condition has length > 1" ?
>
># This is my reproducible code:
>
>#create a vector with the names of the packages I want to use
>packages_i_want_to_use <- c('base',
'this_pac_does_not_exist')
>
># Here I get error messages:
>require( packages_i_want_to_use[1] )
>#Error in if (!loaded) { : the condition has length > 1
>
>require( packages_i_want_to_use[2] )
>#Error in if (!loaded) { : the condition has length > 1
>
># Here I get what I expect:
>require('base')
>
>require('this_pac_does_not_exist')
>#Loading required package: this_pac_does_not_exist
>#Warning message:
>#In library(package, lib.loc = lib.loc, character.only = TRUE,
>logical.return = TRUE,  :
>#  there is no package called ?this_pac_does_not_exist?
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
-- 
Sent from my phone. Please excuse my brevity.