Ah, it works. I was using lapply and it doesn't seem to work. Thank you!----- Original Message -----From: François Pinard Date: Sunday, August 19, 2007 8:36 pmSubject: Re: [R] how to collapse a list of 1 column matrix to a matrix?To: adschai@optonline.netCc: r-help@stat.math.ethz.ch> [adschai@optonline.net]> > >I encounter a situation where I have a list whose element is a > column > >matrix. Says,> > >$'1'> >[,1]> >1> >2> >3> > >$'2'> >[,1]> >4> >5> >6> > >Is there fast way to collapse the list into a matrix like a > cbind > >operation in this case? Meaning, the result should be a matrix > that > >looks like: > > >      [,1]  [,2]> >[1,]    1      4> >[2,]    2      5> >[3,]    3      6> > >I can loop through all elements and do cbind manually. But I > think > >there must be a simpler way that I don't know. Thank you.> > The "do.call" function is the R equivalent of the "apply" from > many > other languages.  I guess that, in R, "apply" was already taken > :-)> For example:> > > a = list(x=matrix(1:3, 3, 1), y=matrix(4:6, 3, 1))> > a> $x>     [,1]> [1,]    1> [2,]    2> [3,]    3> > $y>     [,1]> [1,]    4> [2,]    5> [3,]    6> > > do.call(cbind, a)>     [,1] [,2]> [1,]    1    4> [2,]    2    5> [3,]    3    6> > > -- > François Pinard   http://pinard.progiciels-bpi.ca>

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