[R] Newbie question on using friedman.test()

[Bill Kules]

I am trying to use the friedman.test() on a data frame, d, but
I am receiving the following error message:


> d
   AW HS IAC WA
1   6  8   3  5
2   2  2   3  6
3   7  7   8  3
4   8  5   4  5
....
20  2  5   2  7
21  7  7   6  7
22  7  8   6  8
23  6  8   4  5
24  5  7   5  2
> friedman.test(d)
Error in any(is.na(groups)) : argument "groups" is missing, with no default

I think I just need to convert the data frame to a matrix, and then
friedman.test() will get the roups and blocks automatically.

Question 1) Is my understanding correct?

Question 2) What R function will convert the data frame to the matrix I
need?
I'm still figuring out the matrix functions, and I would appreciate any
pointers or examples.  The help() section is sometimes a bit terse...

Thanks in advance from a Newbie,
Bill

PS - to recreate the above data frame "d":
d <-
structure(list(AW = as.integer(c(6, 2, 7, 8, 8, 8, 7, 5, 3, 6, 
8, 7, 6, 4, 8, 7, 8, 7, 7, 2, 7, 7, 6, 5)), HS = as.integer(c(8, 
2, 7, 5, 4, 5, 7, 7, 2, 8, 4, 7, 8, 7, 6, 7, 5, 8, 8, 5, 7, 8, 
8, 7)), IAC = as.integer(c(3, 3, 8, 4, 7, 5, 8, 3, 4, 3, 7, 4, 
6, 5, 6, 7, 8, 6, 8, 2, 6, 6, 4, 5)), WA = as.integer(c(5, 6, 
3, 5, 3, 6, 7, 8, 3, 5, 6, 7, 7, 7, 7, 6, 4, 7, 8, 7, 7, 8, 5, 
2))), .Names = c("AW", "HS", "IAC", "WA"), row.names = c("1", 
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", 
"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24"
), class = "data.frame")

========
Bill Kules
Principal, Takoma Software, Inc., Takoma Park, MD
  www.takomasoftware.com
Ph.D. Candidate, University of Maryland Human-Computer Interaction Lab
  www.cs.umd.edu/hcil

wmk at takomasoftware.com
(301) 405-2725 voice
(301) 891-7271 voice + voicemail
(301) 891-7273 fax
(301) 755-7982 mobile
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