miceExt (version 1.1.0)

mice.factorize: Transform Imputations of Binarized Data Into Their Corresponding Factors

Description

This function acts as the counterpart to mice.binarize, as it effectively retransforms imputations of binarized data that mice has been run on and that has been post-processed via mice.post.matching after. The post-processing is usually necessary as mice is very likely to impute multiple ones among the dummy columns belonging to to a single factor entry. The resulting mice::mids object is not suited for further mice.mids() iterations or the use of plot, but works well as input to with().

Usage

mice.factorize(obj, par_list)

Arguments

obj

mice::mids object resulting from a call of mice.post.matching() and whose underlying data frame results from a call of mice::binarize().

par_list

List that has been returned in a previous call of mice::binarize() next to the underlying data of the argument obj.

Value

A mice::mids object in which data and imputations have been retransformed from their respective binarized versions in the input obj. As this isn't a proper result of a mice iteration and many of the attributes of obj cannot be transformed well, only the slots data, nmis, where and imp, which are needed in with(), are not NULL. In particular, it would not work as input for mice.mids().

See Also

mice.binarize, mice.post.matching, mice

Examples

# NOT RUN {
# }
# NOT RUN {
#------------------------------------------------------------------------------
# Example that illustrates the combined functionalities of mice.binarize(),
# mice.factorize() and mice.post.matching() on the data set 'boys_data', which
# contains the column blocks ('hgt','bmi') and ('hc','gen','phb') that have
# identical missing value patterns, and out of which the columns 'gen' and
# 'phb' are factors. We are going to impute both tuples blockwise, while
# binarizing the factor columns first. Note that we never need to specify any
# blocks or columns to binarize, as these are all determined automatically 
#------------------------------------------------------------------------------

# By default, mice.binarize() expands all factor columns that contain NAs,
# so the columns 'gen' and 'phb' are automatically binarized
boys_bin <- mice.binarize(boys_data)

# Run mice on binarized data, note that we need to use boys_bin$data to grab
# the actual binarized data and that we use the output predictor matrix
# boys_bin$pred_matrix which is recommended for obtaining better imputation
# models
mids_boys <- mice(boys_bin$data, predictorMatrix = boys_bin$pred_matrix)

# It is very likely that mice imputed multiple ones among one set of dummy
# variables, so we need to post-process. As recommended, we also use the output
# weights from mice.binarize(), which yield a more balanced weighting on the
# column tuple ('hc','gen','phb') within the matching. As in previous examples,
# both tuples are automatically discovered and imputed on
post_boys <- mice.post.matching(mids_boys, weights = boys_bin$weights)

# Now we can safely retransform to the original data, with non-binarized
# imputations
res_boys <- mice.factorize(post_boys$midsobj, boys_bin$par_list)

# Analyze the distribution of imputed variables, e.g. of the column 'gen',
# using the mice version of with()
with(res_boys, table(gen))



#------------------------------------------------------------------------------
# Similar example to the previous, that also works on 'boys_data' and
# illustrates some more advanced funtionalities of all three functions in miceExt: 
# This time we only want to post-process the column block ('gen','phb'), while
# weighting the first of these tuples twice as much as the second. Within the
# matching, we want to avoid matrix computations by using the euclidian distance
# to determine the donor pool, and we want to draw from three donors only.
#------------------------------------------------------------------------------

# Binarize first, we specify blocks in list format with a single block, so we 
# can omit an enclosing list. Similarly, we also specify weights in list format.
# Both blocks and weights will be expanded and can be accessed from the output
# to use them in mice.post.matching() later
boys_bin <- mice.binarize(boys_data, 
                         blocks = c("gen", "phb"), 
                         weights = c(2,1))

# Run mice on binarized data, again use the output predictor matrix from
# mice.binarize()
mids_boys <- mice(boys_bin$data, predictorMatrix = boys_bin$pred_matrix)

# Post-process the binarized columns. We use blocks and weights from the previous
# output, and set 'distmetric' and 'donors' as announced in the example
# description
post_boys <- mice.post.matching(mids_boys,
                               blocks = boys_bin$blocks,
                               weights = boys_bin$weights,
                               distmetric = "euclidian",
                               donors = 3L)

# Finally, we can retransform to the original format
res_boys <- mice.factorize(post_boys$midsobj, boys_bin$par_list)
# }
# NOT RUN {


# }