Map pre/post response pairs to cell indices
response_to_cell(
pre,
post,
has_dk = FALSE,
na_as = c("dk", "missing"),
missing_action = c("omit", "error")
)integer vector of cell indices
character vector of pre-test responses ("0", "1", or "d")
character vector of post-test responses ("0", "1", or "d")
logical; whether model includes don't know
classification of NA responses
structural missingness handling