Summarise a motion-sickness time course

Repeated single-item sickness ratings (FMS, MISC) are collected once a minute and then, almost always, reduced to a handful of per-participant numbers before they are analysed. This produces those numbers: peak, mean, final rating, the area under the rating curve, and when a threshold was first crossed.

Usage

summarize_sickness(data, value, id, time = NULL, by = NULL, threshold = NULL)

Arguments

data

A data frame in long format: one row per rating.

value

Column holding the rating.

id

Column identifying the participant (and, with by, the condition).

time

Optional column holding the time of the rating, in whatever unit the study used. Needed for a meaningful area under the curve and for time-to-threshold; without it, the rating index is used and auc is reported in rating-steps.

by

Optional further grouping columns, e.g. the experimental condition.

threshold

Optional rating at or above which a participant counts as affected, e.g. 6 for MISC (nausea) or 10 for FMS.

Value

A data frame with one row per participant (and by group): n ratings, peak, mean, final, auc (trapezoidal), auc_rate (the AUC divided by the observed duration, i.e. the time-weighted mean rating), and – with threshold – reached and time_to_threshold.

See also

score_questionnaire() for the single-measurement instruments

Examples

d <- data.frame(
  pid = rep(c("p1", "p2"), each = 5),
  minute = rep(0:4, 2),
  fms = c(0, 1, 3, 6, 8, 0, 0, 1, 1, 2)
)
summarize_sickness(d, value = "fms", id = "pid", time = "minute", threshold = 5)
#>   pid n peak mean final auc auc_rate reached time_to_threshold
#> 1  p1 5    8  3.6     8  14     3.50    TRUE                 3
#> 2  p2 5    2  0.8     2   3     0.75   FALSE                NA