[R] Extending each element in a list, or rbind()-ing arrays of different length without recycling

[Gabor Grothendieck]

Try this.  After the apply from your post we use lapply
to make each series into a zoo series so that we can later
use zoo's multiway merge.  Finally we actually merge them
and in the next statement just makes nice column names:

> library(zoo)

> all3 <- do.call(merge, lapply(apply(peaks, 1, unique), zoo))
> colnames(all3) <- make.names(1:ncol(all3))
> all3
  X1 X2 X3
1  2 10  1
2  7  6  9
3  9  8  7
4 NA NA  2
5 NA NA  0


On Thu, Feb 12, 2009 at 2:31 PM, Jason Shaw <jason.shaw.23 at gmail.com> wrote:
> Hi,
>
> I'm trying to take a matrix such as
>
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    2    7    2    7    9
> [2,]   10   10    6    8    6
> [3,]    1    9    7    2    0
>
> and generate a new matrix which contains only the unique values in each row:
>
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    2    7    9   NA   NA
> [2,]   10    6    8   NA   NA
> [3,]    1    9    7    2    0
>
> My problem is that I can use apply(matrix,MARGIN=1,FUN=unique) to find
> the unique values, but this leaves me with a list with arrays of
> different length:
>
>> x <- apply(peaks,MARGIN=1,FUN=unique)
> [[1]]
> [1] 2 7 9
>
> [[2]]
> [1] 10  6  8
>
> [[3]]
> [1] 1 9 7 2 0
>
> and using do.call("rbind",x) recycles the values of the shorter
> vectors instead of filling them with NA:
>
>> do.call("rbind",x)
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    2    7    9    2    7
> [2,]   10    6    8   10    6
> [3,]    1    9    7    2    0
>
> So, I'd like to either take every element of the list and extend it
> with NAs to the length of the longest element, or rbind every element
> where missing places are filled with NAs instead of recycled values.
> Is this possible?  Of course, the solution is trivial using a loop,
> but I'm trying to avoid this.
>
> Thanks for any suggestions.
>
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