R help - May 2004 - for() to lapply()

Hi dear R-users:

I have the following problem:
I have a list of data.frames (12 variables and 60000 rows, each)

I have to merge from an specific point of the list to the
end of the list, I am doing so with a for() loop but it is
too inefficient and it exhausts memory.

How can I convert this for() loop in a function and then use
lapply?
-------------------------------------------------------------
LIST: list of data frames.
m:point of start merging.

result<-merge(LIST[[m]],LIST[[m+1]],by="key",all.x=T)
for (i in (m+2):length(LIST))
{
   result<-merge(result,LIST[[i]],by="key",all.x=T)
}

The problem is the acumulative: "result<-merge(result,...)"

I can think in a function like this:

mergeListelem<-function(i,LS,m)
{
  merge(LS[[m]],LS[[i]],by="key",all.x=T)
}

ind<-m:length(LIST)
lapply(ind,mergeListelem,LIST,m)

But I just obtain a list of merged data.frames,
and I don伮伌t know how to join all the elements
of the list in just one final data.frame.

Thank you for your help

-- 
Kenneth Cabrera
Universidad Nacional de Colombia
Tel Of 430 9351
Cel 315 504 9339
Medell伱伃n

On Thu, May 20, 2004 at 03:52:22PM -0500, Kenneth Cabrera
wrote:
> Hi dear R-users:
> 
> I have the following problem:
> I have a list of data.frames (12 variables and 60000 rows, each)
> 
> I have to merge from an specific point of the list to the
> end of the list, I am doing so with a for() loop but it is
> too inefficient and it exhausts memory.
> 
> How can I convert this for() loop in a function and then use
> lapply?
There's still a better way to do it, I'm sure, but something
like...

##untested!

myMerge <- function(x,y,...) {
	zz <- merge(x,y,...)
	gc()
}

foo <- lapply(my.df.list[[-1]],myMerge,my.df.list[[1]])

Cheers

Jason
-- 
Indigo Industrial Controls Ltd.
http://www.indigoindustrial.co.nz
64-21-343-545
jasont at indigoindustrial.co.nz

> I have the following problem:
> I have a list of data.frames (12 variables and 60000 rows, each)
> 
> I have to merge from an specific point of the list to the
> end of the list, I am doing so with a for() loop but it is
> too inefficient and it exhausts memory.
How about:

a <- list(
	data.frame(a=1),
	data.frame(a=2),
	data.frame(a=3),
	data.frame(a=4)
)
do.call("rbind", a)
do.call("rbind", a[3:4])

(assuming that the data frames have the same variables)

Hadley