Description References Examples
IR-tree models can be fit on the basis of so-called pseudo-items. To this
end, the original, polytomous items are recoded into binary pseudo-items.
Whether a pseudo-item is coded as 1
, 0
, or NA
depends on the model
equations (e.g., Böckenholt, 2012; Plieninger, 2020).
The ItemResponseTrees package internally works with pseudo-items as well.
However, the user has to specify the model equations rather than the
pseudo-items in the irtree_model syntax. Internally, the original responses
are recoded on the basis of the model supplied by the user by the function
irtree_recode()
. This function may also be used directly if desired.
As an alternative to specifying the model equations themselves, users may
also use the function irtree_create_template()
with a mapping matrix (that
specifies the structure of the pseudo-items) to generate the model equations
automatically.
Böckenholt, U. (2012). Modeling multiple response processes in judgment and choice. Psychological Methods, 17(4), 665–678. https://doi.org/10.1037/a0028111
Plieninger, H. (2020). Developing and applying IR-tree models: Guidelines, caveats, and an extension to multiple groups. Organizational Research Methods. Advance online publication. https://doi.org/10.1177/1094428120911096
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | # Mapping matrix for data with three response categories:
(mm <- cbind(cat = 0:2,
p1 = c(0, 1, 1),
p2 = c(NA, 0, 1)))
#> cat p1 p2
#> [1,] 0 0 NA
#> [2,] 1 1 0
#> [3,] 2 1 1
irtree_create_template(data.frame(x1 = 0:2, x2 = 0:2),
mapping_matrix = mm)
#>
#> m1 <- "
#> Equations:
#> 0 = (1-p1)
#> 1 = p1*(1-p2)
#> 2 = p1*p2
#>
#> IRT:
#> p1 BY x1@1, x2@1;
#> p2 BY x1@1, x2@1;
#>
#> Class:
#> Tree
#> "
#>
|
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