String to list and visa versa

Hi,

I need to collapse a list into a string and then reparse it back into the
list.  Normally when I need to do this I simply use write.csv and
read.csv, but I need to do this in memory within R rather than writing out
to file.  Are there any bespoke commands that any knows of that does
something like this or any tips for doing this that anyone can suggest?  I
basically don't care upon the string representation, only that I can
manipulate the list as a string and then reparse it back to a valid list
object.

Many thanks for your help,

Tom

On Tuesday 14 November 2006 12:00 pm, Tom McCallum wrote:

Hi,

I need to collapse a list into a string and then reparse it back into the
list.  Normally when I need to do this I simply use write.csv and
read.csv, but I need to do this in memory within R rather than writing out
to file.  Are there any bespoke commands that any knows of that does
something like this or any tips for doing this that anyone can suggest?  I
basically don't care upon the string representation, only that I can
manipulate the list as a string and then reparse it back to a valid list
object.

#List -> string:

#
# Put whatever you want into collapse to separate list entries
#
paste(unlist(L), collapse=",")

#String->list
strsplit(S, ",")

               best

                  Vladimir Dergachev

Many thanks for your help,

Tom

Hi,

I need to collapse a list into a string and then reparse it back into the  
list.  Normally when I need to do this I simply use write.csv and  
read.csv, but I need to do this in memory within R rather than writing out  
to file.  

Are there any bespoke commands that any knows of that does  
something like this or any tips for doing this that anyone can
suggest?

 I  
basically don't care upon the string representation, only that I can  
manipulate the list as a string and then reparse it back to a valid list  
object.

This approach won't work in very many cases (but then nor will write.csv).

The safest way I know is to use serialize() and unserialize().  Next to
that, deparse(control="all") and parse(text=) are quite good and give a
human-readable character representation.

If fidelity is not the main issue, as.character and toString spring to
mind.  unlist is recursive, and is not going to come close to being
faithful for other than very simple lists. And what if ',' is a character
in one of the list elements?

On Tuesday 14 November 2006 12:28 pm, Prof Brian Ripley wrote:

This approach won't work in very many cases (but then nor will write.csv).

The safest way I know is to use serialize() and unserialize().  Next to
that, deparse(control="all") and parse(text=) are quite good and give a
human-readable character representation.

If fidelity is not the main issue, as.character and toString spring to
mind.  unlist is recursive, and is not going to come close to being
faithful for other than very simple lists. And what if ',' is a character
in one of the list elements?

Yes, but then one can replace ',' with something rarely used like \007.
I picked ',' because write.csv/read.csv worked before.

You are right, for storage serialize/unserialize seem best, however for
manipulation one would usually prefer a well-defined format.

On Tue, 14 Nov 2006, Vladimir Dergachev wrote:

On Tuesday 14 November 2006 12:28 pm, Prof Brian Ripley wrote:

This approach won't work in very many cases (but then nor will  
write.csv).

The safest way I know is to use serialize() and unserialize().  Next to
that, deparse(control="all") and parse(text=) are quite good and give a
human-readable character representation.

If fidelity is not the main issue, as.character and toString spring to
mind.  unlist is recursive, and is not going to come close to being
faithful for other than very simple lists. And what if ',' is a  
character
in one of the list elements?

Yes, but then one can replace ',' with something rarely used like \007.
I picked ',' because write.csv/read.csv worked before.

But it quotes strings ....

You are right, for storage serialize/unserialize seem best, however for
manipulation one would usually prefer a well-defined format.