Dear all,
I have a question concerning my output of the dunn.test function in R. I
like to compare different datasets, which are not distributed normally, so
I use the Dunn.test to do pairwise comparison. I have 2 questions
concerning the output:
- why are my groupnames changed, the output gives 4 times swirskii,
although my groupnames are longer (see my dataset)
- secondly when I check the p-values, I see something very odd: I see that
p values where the same groups are compared sometimes indicate that they
are different, why are not all those p-values = 1 ?
This is my dataset:
structure(list(controle = c(111, 88, 216, 169), chemie = c(47, 31, 35,
30), IPM = c(0, 0, 0, 1), gallicus = c(102, 152, 102, 75), swirskii3 =
c(1, 0, 0, 0), swirskiiA = c(0, 0, 1, 3), swirskiiP = c(0, 0, 1, 6),
swirskii1x = c(12, 2, 75, 46)), .Names = c("controle",
"chemie", "IPM",
"gallicus", "swirskii3", "swirskiiA",
"swirskiiP", "swirskii1x"),
row.names = c(NA, 4L), class = "data.frame")
I get the following output:
DUNN <- dunn.test(value, variable, method = "none",kw=TRUE)
Kruskal-Wallis rank sum test
data: value and variable
Kruskal-Wallis chi-squared = 26.8894, df = 7, p-value = 0
Comparison of value by variable
(No adjustment)
Col Mean-|
Row Mean | controle chemie IPM gallicus swirskii swirskii
---------+------------------------------------------------------------------
chemie | -1.341044 -3.410083 -2.069039 -0.325682 1.015361 3.084401
| 0.0900 0.0003 0.0193 0.3723 0.1550 0.0010
|
IPM | -3.410083 -2.069039 -0.325682 1.015361 3.084401
-3.410083
| 0.0003 0.0193 0.3723 0.1550 0.0010 0.0003
|
gallicus | -0.325682 1.015361 3.084401 -3.410083 -2.069039 0.000000
| 0.3723 0.1550 0.0010 0.0003 0.0193 0.5000
|
swirskii | -3.410083 -2.069039 0.000000 -3.084401 -3.007770
-1.666726
| 0.0003 0.0193 0.5000 0.0010 0.0013 0.0478
|
swirskii | -3.007770 -1.666726 0.402313 -2.682088 0.402313
-2.969454
| 0.0013 0.0478 0.3437 0.0037 0.3437
0.0015
|
swirskii | -2.969454 -1.628410 0.440628 -2.643772 0.440628 0.038315
| 0.0015 0.0517 0.3297 0.0041 0.3297 0.4847
|
swirskii | -1.475148 -0.134104 1.934935 -1.149466 1.934935 1.532621
| 0.0701 0.4467 0.0265 0.1252 0.0265 0.0627
Col Mean-|
Row Mean | swirskii
---------+-----------
chemie | -3.410083
| 0.0003
|
IPM | -2.069039
| 0.0193
|
gallicus | -3.084401
| 0.0010
|
swirskii | 0.402313
| 0.3437
|
swirskii | -1.628410
| 0.0517
|
swirskii | -1.475148
| 0.0701
|
swirskii | 1.494306
| 0.0675
Met vriendelijke groeten - With kind regards,
Joachim Audenaert
onderzoeker gewasbescherming - crop protection researcher
PCS | proefcentrum voor sierteelt - ornamental plant research
Schaessestraat 18, 9070 Destelbergen, Belgi?
T: +32 (0)9 353 94 71 | F: +32 (0)9 353 94 95
E: joachim.audenaert at pcsierteelt.be | W: www.pcsierteelt.be
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