R help - Sep 2003 - Converting character to function argument

How can one transform a character string into an argument of a function
(which is not or I don't want it to be a character string)?

Example:
> expand.grid(c(1,0),c(1,0)) ## OK
  Var1 Var2
1    1    1
2    0    1
3    1    0
4    0    0

> paste(rep("c(0,1)",2),collapse=',') ## to be used below
[1] "c(0,1),c(0,1)"
> ## string is the input I want, but it needs to be coerced to the correct
format
> expand.grid(paste(rep("c(0,1)",2),collapse=',')) ## does
not get me there
           Var1
1 c(0,1),c(0,1)

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Have you considered

	 eval(parse(text="expand.grid(c(1,0),c(1,0))"))

There are other ways to get what you want, but this should work.

hope this helps.  spencer graves

Alvaro.Antonio.Novo at bportugal.pt wrote:
> How can one transform a character string into an argument of a function
> (which is not or I don't want it to be a character string)?
> 
> Example:
> 
> 
>>expand.grid(c(1,0),c(1,0)) ## OK
> 
>   Var1 Var2
> 1    1    1
> 2    0    1
> 3    1    0
> 4    0    0
> 
> 
> 
>>paste(rep("c(0,1)",2),collapse=',') ## to be used
below
> 
> [1] "c(0,1),c(0,1)"
> 
>>## string is the input I want, but it needs to be coerced to the correct
> 
> format
> 
> 
>>expand.grid(paste(rep("c(0,1)",2),collapse=',')) ##
does not get me there
> 
>            Var1
> 1 c(0,1),c(0,1)
> 
> ***************************************************************************
>  AVISO DE CONFIDENCIALIDADE: Esta mensagem, assim como os ficheiros
> eventualmente anexos, ? confidencial e reservada apenas ao conhecimento
> da(s) pessoa(s) nela indicada(s) como destinat?ria(s). Se n?o ? o seu
> destinat?rio, solicitamos que n?o fa?a qualquer uso do respectivo conte?do
> e proceda ? sua destrui??o, notificando o remetente.
>  LIMITA??O DE RESPONSABILIDADE: A seguran?a da transmiss?o de informa??o
> por via electr?nica n?o pode ser garantida pelo remetente, o qual, em
> consequ?ncia, n?o se responsabiliza por qualquer facto suscept?vel de
> afectar a sua integridade.
> 
>  CONFIDENTIALITY NOTICE: This message, as well as existing attached files,
> is confidential and intended exclusively for the individual(s) named as
> addressees. If you are not the intended recipient, you are kindly requested
> not to make any use whatsoever of its contents and to proceed to the
> destruction of the message, thereby notifying the sender.
>  DISCLAIMER: The sender of this message can not ensure the security of its
> electronical transmission and consequently does not accept liability for
> any fact which may interfere with the integrity of its content.
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

eval() and parse() are you friends here. Possibly also substitute().
Example:

 eval(parse(text="expand.grid(c(1,0),c(1,0))"))

However, I would like to reply with a question to you. Why do you end up
with a string that you need to convert in the first place? Maybe you are
more interested in a solution like the following one:

N <- 2
l <- lapply(1:N, FUN=function(x) c(0,1))
expand.grid(l)

Henrik Bengtsson
Lund University
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Alvaro.Antonio.Novo at bportugal.pt
> Sent: den 12 september 2003 18:55
> To: r-help at stat.math.ethz.ch
> Subject: [R] Converting character to function argument
> 
> 
> How can one transform a character string into an argument of 
> a function (which is not or I don't want it to be a character string)?
> 
> Example:
> 
> > expand.grid(c(1,0),c(1,0)) ## OK
>   Var1 Var2
> 1    1    1
> 2    0    1
> 3    1    0
> 4    0    0
> 
> 
> > paste(rep("c(0,1)",2),collapse=',') ## to be used
below
> [1] "c(0,1),c(0,1)"
> > ## string is the input I want, but it needs to be coerced to the 
> > correct
> format
> 
> > expand.grid(paste(rep("c(0,1)",2),collapse=',')) ##
does not get me
> > there
>            Var1
> 1 c(0,1),c(0,1)
> 
> **************************************************************
> *************
>  AVISO DE CONFIDENCIALIDADE: Esta mensagem, assim como os 
> ficheiros eventualmente anexos, ? confidencial e reservada 
> apenas ao conhecimento
> da(s) pessoa(s) nela indicada(s) como destinat?ria(s). Se n?o 
> ? o seu destinat?rio, solicitamos que n?o fa?a qualquer uso 
> do respectivo conte?do e proceda ? sua destrui??o, 
> notificando o remetente.  LIMITA??O DE RESPONSABILIDADE: A 
> seguran?a da transmiss?o de informa??o por via electr?nica 
> n?o pode ser garantida pelo remetente, o qual, em 
> consequ?ncia, n?o se responsabiliza por qualquer facto 
> suscept?vel de afectar a sua integridade.
> 
>  CONFIDENTIALITY NOTICE: This message, as well as existing 
> attached files, is confidential and intended exclusively for 
> the individual(s) named as addressees. If you are not the 
> intended recipient, you are kindly requested not to make any 
> use whatsoever of its contents and to proceed to the 
> destruction of the message, thereby notifying the sender.
>  DISCLAIMER: The sender of this message can not ensure the 
> security of its electronical transmission and consequently 
> does not accept liability for any fact which may interfere 
> with the integrity of its content.
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list 
> https://www.stat.math.ethz.ch/mailman/listinfo> /r-help
> 
>