R help - Jan 2005 - Parallel computations using snow: how to combine boot objects?

Hello,

I'm trying to do some bootstrapping in a parallel environment (Linux
cluster) in order to estimate confidence intervals for a certain
parameter. Following the example in the documentation of the "snow"
package (http://www.stat.uiowa.edu/~luke/R/cluster/cluster.html), I
launch my computations by something like
> cl.nuke.boot <-
+             clusterCall(cl,boot,nuke.data, nuke.fun, R=500, m=1,
+                         fit.pred=new.fit, x.pred=new.data)

which gives me a list of n boot objects (where n is the number of nodes
in my cluster). So far, so good.

However, if I now want to go further, I need to combine all these boot
objects to a single one which I can pass to boot.ci for example. Is
there a recommended way to do this?

Thanks,
Michael

Take a look at the utility function in snow called something like 
clusterSplit.

The example ducks that issue. Someone needs to write a function for
merging these results.  Probably just involves making a suitable call
to boot.return, which is what happens at the end of boot(), but I
don't know if anyone has actually done this yet.

luke

On Fri, 21 Jan 2005, BEER Michael wrote:
> Hello,
> 
> I'm trying to do some bootstrapping in a parallel environment (Linux
> cluster) in order to estimate confidence intervals for a certain
> parameter. Following the example in the documentation of the
"snow"
> package (http://www.stat.uiowa.edu/~luke/R/cluster/cluster.html), I
> launch my computations by something like
> 
> > cl.nuke.boot <-
> +             clusterCall(cl,boot,nuke.data, nuke.fun, R=500, m=1,
> +                         fit.pred=new.fit, x.pred=new.data)
> 
> which gives me a list of n boot objects (where n is the number of nodes
> in my cluster). So far, so good.
> 
> However, if I now want to go further, I need to combine all these boot
> objects to a single one which I can pass to boot.ci for example. Is
> there a recommended way to do this?
> 
> Thanks,
> Michael
> 
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-- 
Luke Tierney
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
   Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu