exogenize function

Structural Mapping for an IRTree Model

Expands a wide-form file of item responses to a long-form file supporting structural mappings among latent variables

exogenize(mat, cmx, items=seq_len(ncol(mat)), endnode, crossitem=NULL)

Arguments

• mat: An integer matrix of IRT responses (columns represent items, rows represent respondents)

• cmx: The mapping matrix.

• items: A numeric vector with the column positions of all items (measurement variables) in mat. Defaults to all columns of mat.

• endnode: A factor with the same length as items

  indicating the latent variable to which the item is attached, and compatible with the mapping matrix.

• crossitem: A factor with the same length as items

  indicating the original items that have been crossed with endnode (e.g., given at various occasions over time), thus producing the actual items. This is not meaningful when the design is nested, and should better be omitted in such cases.

Returns

A data frame with columns: - person: a factor identifying the respondent;

• item: a factor identifying the items;

• exo1 to exoS: dummy variables identifying the internal nodes: these play the same role as exofactor but are necessary when the model must include independent random effects;

• endnode: a factor identifying the end nodes and thus the endogeneous latent variables;

• crossitem: a factor produced only for crossed designs, identifying the items that are crossed with endnode, for example, in the case when the same items are repeated over time in a longitudinal design;

• value: the binary item responses.

References

De Boeck, P. and Partchev, I. (2012). IRTrees: Tree-Based Item Response Models of the GLMM Family, Journal of Statistical Software -- Code Snippets, 48 (1), 1--28. https://www.jstatsoft.org/v48/c01/.

Author(s)

Ivailo Partchev

See Also

dendrify

Examples

str(linlatT <- exogenize(linlat, 
   cbind(c(1,0,0), c(1,1,0), c(0,1,0), c(0,1,1), c(0,0,1)),
   endnode = rep(1:3, each=10), cross = rep(1:10, 3)))