[R] lexicographic sort of ordered lists

Spencer Graves spencer.graves at pdf.com
Fri Jul 18 22:30:15 CEST 2003


"?order"?

J. P. Morgan wrote:
> Does anyone know how to execute the following sort problem in R? Matrix X
> has positive integer entries, and each column has been sorted in ascending
> order. The problem is now to order the columns lexicographically. For
> instance if the matrix X is
> 
>  
> 
> 1 2 1 1 2
> 
> 2 2 3 3 2
> 
> 3 5 5 4 2
> 
>  
> 
> then the result should be
> 
>  
> 
> 1 1 1 2 2
> 
> 2 3 3 2 2
> 
> 3 4 5 2 5
> 
>  
> 
> Let ONE be a vector of 1's of length ncol(X). The result in this example can
> be accomplished by
> 
>  
> 
> X=X[,order(ONE,X[1,],X[,2],X[,3])]
> 
>  
> 
> but I need a method that will work regardless of k=number of rows of X. That
> is, the program must be able to accept any integer-valued matrix X for which
> each column is sorted, then permute columns accordingly. 
> 
>  
> 
> Thanks, JP
> 
>  
> 
>  
> 
> 
> 	[[alternative HTML version deleted]]
> 
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