[R] Help with a more flexible funtion for multiple comparision of means

From: Jose Claudio Faria <joseclaudio.faria_at_terra.com.br>
Date: Mon 12 Sep 2005 - 13:27:36 EST


Dear R-list,

Could anybody tell me (or give me a tip) of how to implement the Duncan distribution in R?

I've been trying to make a new and more flexible function for multiple comparison of means: Tukey, SNK and Duncan, from 'aov' objects, like TukeyHSD function.

For while, it is running nice (Tukey and SNK), for simple design (completely randomized, randomized block and Latin squares) and simple experimental schemes   (one factor).

I'm needing only two informations: 'qduncan' and 'pduncan', similar to already available in R 'qtukey' and 'ptukey'. The basic algorithm implemented with SNK test will be used for Duncan test.

Below a sample:
a) Generating data and calling the function:

tra = gl(4, 5, label = c('A', 'B', 'C', 'D')) blo = rep(1:5, 4)
pro = c(NA, 26, 20, 23, 21, 31, 25, 28, 27, 24, 22, 26, NA, 25, 29, 33, 29, 31, 34, NA)

x = aov(pro ~ tra) #or x= aov(pro ~ blo + tra) res = mctm(x, which='tra', test='SNK', conf.level=0.95) print(res)

b) The R output:

$Table

Tables of means
Grand mean

26.70588

  tra

        A  B    C     D
     22.5 27 25.5 31.75

rep 4.0 5 4.0 4.00

$Ordered means

tra

     D B C A
31.75 27.00 25.50 22.50

$Result

   D B C A
D - * * *

B *  - ns ns
C * ns  - ns
A * ns ns  -

$Test

[1] "SNK"
$Conf.level

[1] 0.95

$Mean differences

      D B C A

D 0.00 4.75 6.25 9.25
B 4.75 0.00 1.50 4.50
C 6.25 1.50 0.00 3.00
A 9.25 4.50 3.00 0.00


$Minimum Significative Differences - MSD
D B C A D 0.00 3.83 4.93 5.48 B 3.83 0.00 3.83 4.68

C 4.93 3.83 0.00 4.04
A 5.48 4.68 4.04 0.00

$Replicates number

     D B C A

D   - 4:5 4:4 4:4
B 5:4   - 5:4 5:4
C 4:4 4:5   - 4:4

A 4:4 4:5 4:4 -

Thanks in advance,

-- 
Jose Claudio Faria
Brasil/Bahia/UESC/DCET
Estatistica Experimental/Prof. Adjunto
mails:
  joseclaudio.faria@terra.com.br
  jc_faria@uesc.br
  jc_faria@uol.com.br
tel: 73-3634.2779

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Received on Mon Sep 12 13:32:54 2005

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