construct.blocks {mice}

Construct blocks from formulas and predictorMatrix

Description

This helper function attempts to find blocks of variables in the specification of the formulas and/or predictorMatrix objects. Blocks specified by formulas may consist of multiple variables. Blocks specified by predictorMatrix are assumed to consist of single variables. Any duplicates in names are removed, and the formula specification is preferred. predictorMatrix and formulas. When both arguments specify models for the same block, the model for the predictMatrix is removed, and priority is given to the specification given in formulas.

Usage

construct.blocks(formulas = NULL, predictorMatrix = NULL)

Arguments

formulas

A named list of formula's, or expressions that can be converted into formula's by as.formula. List elements correspond to blocks. The block to which the list element applies is identified by its name, so list names must correspond to block names. The formulas argument is an alternative to the predictorMatrix argument that allows for more flexibility in specifying imputation models, e.g., for specifying interaction terms.

predictorMatrix

A numeric matrix of length(blocks) rows and ncol(data) columns, containing 0/1 data specifying the set of predictors to be used for each target column. Each row corresponds to a variable block, i.e., a set of variables to be imputed. A value of 1 means that the column variable is used as a predictor for the target block (in the rows). By default, the predictorMatrix is a square matrix of ncol(data) rows and columns with all 1's, except for the diagonal. Note: For two-level imputation models (which have "2l" in their names) other codes (e.g, 2 or -2) are also allowed.

Value

A blocks object.

See Also

make.blocks, name.blocks

Examples

form <- name.formulas(list(bmi + hyp ~ chl + age, chl ~ bmi))
pred <- make.predictorMatrix(nhanes[, c("age", "chl")])
construct.blocks(formulas = form, pred = pred)