[R] matching values in a list

[Gabor Grothendieck]

The first line was missing.  It should be:

mat <- do.call(rbind, a)
sapply(apply(mat, 2, table), function(x) mean(as.numeric(names(x))[x
== length(a)]))


On Jan 11, 2008 7:23 PM, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> Assume that no component matrix can have repeated values.
>
> First we apply table to mat yielding a list of named counts.
> To each component of that we sapply the indicated function
> which picks out those that occur length(a) times (so they are
> in every column), converts the name to numeric and averages
> them.
>
> sapply(apply(mat, 2, table), function(x) mean(as.numeric(names(x))[x
> == length(a)]))
>
> By the way, note that the a you define is slightly different from the
> a displayed in your post.
>
>
> On Jan 11, 2008 6:09 PM, dxc13 <dxc13 at health.state.ny.us> wrote:
> >
> > useR's,
> >
> > I want to match the real number elements of a list that has 3 matrices as
> > its elements and then average those numbers.  I think I am close, but I
> > can't get it to quite work out.  For example,
> >
> > > a <- list(matrix(c(10,NA,NA,12,11,
> > > 10,13,NA,14,12),ncol=2),matrix(c(10,12,15,13,11,
> > > 13,NA,NA,12,10),ncol=2),matrix(c(10,15,NA,13,NA, 13,12,NA,NA,10),ncol=2))
> > > a
> > [[1]]
> >     [,1] [,2]
> > [1,]   10   10
> > [2,]   NA   13
> > [3,]   NA   NA
> > [4,]   13   14
> > [5,]   11   12
> >
> > [[2]]
> >     [,1] [,2]
> > [1,]   10   13
> > [2,]   12   NA
> > [3,]   15   NA
> > [4,]   13   12
> > [5,]   11   10
> >
> > [[3]]
> >     [,1] [,2]
> > [1,]   10   13
> > [2,]   15   12
> > [3,]   NA   NA
> > [4,]   13   NA
> > [5,]   NA   10
> >
> > I want to average the non-NA numbers that simultaneously appear in each
> > column of all 3 matrices.  For the first column, 10 and 13 are the only
> > numbers that appear in all 3 matrices.  Thus, I want to take the average of
> > 10 and 13.  Then repeat the same process for the second column.  The data
> > here is only a sample, but with the data I work with, there are many more
> > columns in each matrix in the list.  Does anyone know a efficient way to do
> > this?  Maybe using lapply()?  Thanks in advance.
> >
> > dxc13
> > --
> > View this message in context: http://www.nabble.com/matching-values-in-a-list-tp14767170p14767170.html
> > Sent from the R help mailing list archive at Nabble.com.
> >
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> >
>