R help - Nov 2015 - Problems using save to store NAMED R objects

I have to store (in a file) an R object that was created with is name as 
a string of characters, as follows:

   : nn <- "xxx"
   : assign(nn, 5)
   : xxx
   [1] 5

I don't want to store the object nn but the object xxx. I tried the 
following two expressions but none of them worked:

   : save(get(nn), file="f.RData")
   Error in save(get(nn), file = "f.RData") : object ?get(nn)? not
found

   : save(eval(nn), file="f.RData")
   Error in save(eval(nn), file = "f.RData") : object ?eval(nn)? not 
found

I know that both save(xxx, ..), and save("xxx", ..) work, but the fact
is that the string is going to be provided by an user:

   : nn <- readline("Your variable->")

and 
   : save(nn, file="f.RData")
stores the objet nn not xxx

Do you have any comments on this?

Thanks

  -Sergio.

On 12/11/2015 6:41 PM, Julio Sergio Santana wrote:
> I have to store (in a file) an R object that was created with is name as
> a string of characters, as follows:
>
>     : nn <- "xxx"
>     : assign(nn, 5)
>     : xxx
>     [1] 5
>
> I don't want to store the object nn but the object xxx. I tried the
> following two expressions but none of them worked:
>
>     : save(get(nn), file="f.RData")
>     Error in save(get(nn), file = "f.RData") : object ?get(nn)?
not found
>
>     : save(eval(nn), file="f.RData")
>     Error in save(eval(nn), file = "f.RData") : object ?eval(nn)?
not
> found
>
> I know that both save(xxx, ..), and save("xxx", ..) work, but the
fact
> is that the string is going to be provided by an user:
>
>     : nn <- readline("Your variable->")
>
> and
>     : save(nn, file="f.RData")
> stores the objet nn not xxx
>
> Do you have any comments on this?
I believe

do.call(save, list(as.name(nn), file = "f.RData"))

should do what you want.  There are probably other ways, maybe simpler 
ones.

If you're interested, the theory here is that do.call() constructs a 
call to the first argument, with arguments found by evaluating the 
second argument.

Duncan Murdoch

Thanks Duncan,

I just saw another, but similar, solution for this in
http://stackoverflow.com/questions/11084395/save-object-using-variable-with-object-name
,
and it is:

   : save(list=nn, file="f.RData")

Thanks again,

  -Sergio.

On Thu, Nov 12, 2015 at 8:57 PM, Duncan Murdoch <murdoch.duncan at
gmail.com>
wrote:
> On 12/11/2015 6:41 PM, Julio Sergio Santana wrote:
>
>> I have to store (in a file) an R object that was created with is name
as
>> a string of characters, as follows:
>>
>>     : nn <- "xxx"
>>     : assign(nn, 5)
>>     : xxx
>>     [1] 5
>>
>> I don't want to store the object nn but the object xxx. I tried the
>> following two expressions but none of them worked:
>>
>>     : save(get(nn), file="f.RData")
>>     Error in save(get(nn), file = "f.RData") : object
?get(nn)? not found
>>
>>     : save(eval(nn), file="f.RData")
>>     Error in save(eval(nn), file = "f.RData") : object
?eval(nn)? not
>> found
>>
>> I know that both save(xxx, ..), and save("xxx", ..) work, but
the fact
>> is that the string is going to be provided by an user:
>>
>>     : nn <- readline("Your variable->")
>>
>> and
>>     : save(nn, file="f.RData")
>> stores the objet nn not xxx
>>
>> Do you have any comments on this?
>>
>
> I believe
>
> do.call(save, list(as.name(nn), file = "f.RData"))
>
> should do what you want.  There are probably other ways, maybe simpler
> ones.
>
> If you're interested, the theory here is that do.call() constructs a
call
> to the first argument, with arguments found by evaluating the second
> argument.
>
> Duncan Murdoch
>


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Julio Sergio Santana
Instituto Mexicano de Tecnolog?a del Agua
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