Filter to Cases of Interest — filter

filter_crf() filters out cases which have previously answered the survey or were not at work within days days of their onset/test date.

filter_crf(data = download_crf(), days = 5L, na_keep = TRUE)

Arguments

data	A data frame with data from the CRF REDcap project, as output by `download_crf()`
days	The maxmimum allowed difference between last day worked (`last_worked`) and test date (`specimendate`)
na_keep	Should missing data be kept or excluded?

The input data filtered according to the description above