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

[Patrick Burns]

My question is: Why would you want a data
structure that is clearly not expressive of the
data involved?

Let me guess.  You are coming from statistical
software where data are always rectangular.


Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of "The R Inferno" and "A Guide for the Unwilling S User")

Jason Shaw 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.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
>