R help - Mar 2006 - converting a string to a vector without using strsplit and unlink?

Hi

I am importing some data from a postgres database and one of the fields 
contains an array of values. This field is in the form "{1,2,3,4,5}"
and
is imported as a character string into "R".  I am able to convert the 
string into a vector of numerics using the strsplit and unlist 
functions, but I find that a very inelegant (and slow) solution.
As an alternative I have coaxed the database into exporting the data in 
the form "c(1,2,3,4,5)" and importing that into R. Unfortunately this
is
also interpreted as one long character string instead of a vector 
containing values. If I edit the corresponding fields in the table with 
the "edit" command and remove the quotes at the beginning and end of
the
line, the data is recognized as a vector of numerics.

Question: Is there any direct or easy way of converting a string 
"c(1,2,3,4,5)" into a vector of values without going through 
strsplit&unlist and/or is there a way to import arrays from postgres 
directly as arrays or vectors and not strings (and thereby avoid all the 
trouble in the first place).


Best wishes

Tancred

Try this:

x <- "c(1,2)"
eval(parse(text = x))

or

x <- sub("\\{(.*)\\}", "c(\\1)", "{1,2,3,4,5}")
eval(parse(text = x))

or

scan(textConnection(gsub("[{}]", "",
"{1,2,3,4,5}")), sep = ",")

On 3/21/06, Tancred Frickey <tancred.frickey at rsbs.anu.edu.au>
wrote:
> Hi
>
> I am importing some data from a postgres database and one of the fields
> contains an array of values. This field is in the form
"{1,2,3,4,5}" and
> is imported as a character string into "R".  I am able to convert
the
> string into a vector of numerics using the strsplit and unlist
> functions, but I find that a very inelegant (and slow) solution.
> As an alternative I have coaxed the database into exporting the data in
> the form "c(1,2,3,4,5)" and importing that into R. Unfortunately
this is
> also interpreted as one long character string instead of a vector
> containing values. If I edit the corresponding fields in the table with
> the "edit" command and remove the quotes at the beginning and end
of the
> line, the data is recognized as a vector of numerics.
>
> Question: Is there any direct or easy way of converting a string
> "c(1,2,3,4,5)" into a vector of values without going through
> strsplit&unlist and/or is there a way to import arrays from postgres
> directly as arrays or vectors and not strings (and thereby avoid all the
> trouble in the first place).
>
>
> Best wishes
>
> Tancred
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>

Many thanks. That does it

Gabor Grothendieck wrote:
>Try this:
>
>x <- "c(1,2)"
>eval(parse(text = x))
>
>or
>
>x <- sub("\\{(.*)\\}", "c(\\1)",
"{1,2,3,4,5}")
>eval(parse(text = x))
>
>or
>
>scan(textConnection(gsub("[{}]", "",
"{1,2,3,4,5}")), sep = ",")
>
>On 3/21/06, Tancred Frickey <tancred.frickey at rsbs.anu.edu.au>
wrote:
>  
>
>>Hi
>>
>>I am importing some data from a postgres database and one of the fields
>>contains an array of values. This field is in the form
"{1,2,3,4,5}" and
>>is imported as a character string into "R".  I am able to
convert the
>>string into a vector of numerics using the strsplit and unlist
>>functions, but I find that a very inelegant (and slow) solution.
>>As an alternative I have coaxed the database into exporting the data in
>>the form "c(1,2,3,4,5)" and importing that into R.
Unfortunately this is
>>also interpreted as one long character string instead of a vector
>>containing values. If I edit the corresponding fields in the table with
>>the "edit" command and remove the quotes at the beginning and
end of the
>>line, the data is recognized as a vector of numerics.
>>
>>Question: Is there any direct or easy way of converting a string
>>"c(1,2,3,4,5)" into a vector of values without going through
>>strsplit&unlist and/or is there a way to import arrays from postgres
>>directly as arrays or vectors and not strings (and thereby avoid all the
>>trouble in the first place).
>>
>>
>>Best wishes
>>
>>Tancred
>>
>>______________________________________________
>>R-help at stat.math.ethz.ch mailing list
>>https://stat.ethz.ch/mailman/listinfo/r-help
>>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>>
>>    
>>