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rank of a matrix

4 messages · mingan, Spencer Graves, Uwe Ligges +1 more

Original
mingan
# 
how do I check the rank of a matrix ?

say

A=  1   0   0
     0   1   0

then rank(A)=2

what is this function?

thanks


  I did try help.search("rank"), but all the returned help information 
seem irrelevant to what I want.

  I would like to know how people search for help information like this.






rank(base)              Sample Ranks
SignRank(stats)         Distribution of the Wilcoxon Signed Rank
                        Statistic
Wilcoxon(stats)         Distribution of the Wilcoxon Rank Sum
                        Statistic
friedman.test(stats)    Friedman Rank Sum Test
kruskal.test(stats)     Kruskal-Wallis Rank Sum Test
pairwise.wilcox.test(stats)
                        Pairwise Wilcoxon rank sum tests
wilcox.test(stats)      Wilcoxon Rank Sum and Signed Rank Tests
Spencer Graves
# 
Have you considered something like the following:

matrix.rank <- function(A, eps=sqrt(.Machine$double.eps)){
	sv. <- abs(svd(A)$d)
	sum((sv./max(sv.))>eps)
}

matrix.rank(A=diag(3))
#[1] 3
A <- array(c(1,1,0,0), dim=c(2,2))
matrix.rank(A)
#[1] 1
mingan wrote:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Uwe Ligges
    

    

      
      #
    

  


  

      
mingan wrote:

        

            

      
      
      
    

        
Well, calculating the rank is from the computational point of view a 
very hard problem.
See ?qr

Uwe Ligges

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Sundar Dorai-Raj
    

    

      
      #
    

  


  

      
mingan wrote on 5/4/2005 8:54 AM:

            

      
      
      
    

        

      
      
    

        
See ?qr or ?svd.

tol <- 1e-7
qr(A, tol)$rank
sum(svd(A)$d > tol)

--sundar