Error in dunntest: Error in if (tmp$Eclass != "factor") { : the condition has length > 1

Question

I get an error when I try to run the Dunntest on my data and I can't figure out what's causing it.

I have 4 groups with ordinal discrete data, the Kruskal-Wallis test suggest a significant difference between groups but I can't run the dunntest afterwards.

Any help is appreciated.

> mast_cells
# A tibble: 20 × 2
   group score
   <ord> <dbl>
 1 1         1
 2 1         1
 3 1         1
 4 1         1
 5 1         1
 6 2         3
 7 2         4
 8 2         2
 9 2         1
10 2         3
11 3         2
12 3         1
13 3         2
14 3         3
15 3         3
16 4         3
17 4         2
18 4         3
19 4         2
20 4         2
> mast_cells$group <- ordered(mast_cells$group ,
+                             levels = c("1", "2", "3", "4"))
> kruskal.test( score ~ group, data = mast_cells)

    Kruskal-Wallis rank sum test

data:  score by group
Kruskal-Wallis chi-squared = 9.1875, df = 3, p-value = 0.0269

> library(FSA)
> dunnTest(score ~ group,
+          data = mast_cells,
+          method="Benjamini-Yekuteili")
Error in if (tmp$Eclass != "factor") { : the condition has length > 1
>

Artem · Accepted Answer · 2022-12-14T09:58:52.730

dunTest function does not accept formula as an argument, you need specify your data vector as the first argument, and factor as the second one. Additionally if you choose Benjamini-Yekuteili adjustement method for multiple comparison, option method = "by" should be specified.

See the code below:

library(FSA)

mast_cells <- structure(
  list(group = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 2L, 
    2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L), 
    levels = c("1", "2", "3", "4"), class = c("ordered", "factor")), 
  score = c(1L, 1L, 1L, 1L, 1L, 3L, 4L, 2L, 1L, 3L, 
    2L, 1L, 2L, 3L, 3L, 3L, 2L, 3L, 2L, 2L)), 
  row.names = c("1", "2", "3", "4", "5", "6", "7", "8", "9", "10", 
                "11", "12", "13", "14", "15", "16", "17", "18", "19", "20"), 
  class = "data.frame")


dunnTest(mast_cells$score, mast_cells$group, method = "by")

Output:

Dunn (1964) Kruskal-Wallis multiple comparison
  p-values adjusted with the Benjamini-Yekuteili method.

  Comparison          Z     P.unadj      P.adj
1      1 - 2 -2.6685305 0.007618387 0.11199029
2      1 - 3 -2.1348244 0.032775359 0.16059926
3      2 - 3  0.5337061 0.593544894 1.00000000
4      1 - 4 -2.4999917 0.012419622 0.09128422
5      2 - 4  0.1685388 0.866159449 1.00000000
6      3 - 4 -0.3651673 0.714986507 1.00000000

Error in dunntest: Error in if (tmp$Eclass != "factor") { : the condition has length > 1

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