The function meal_metrics calculates three simple glucose meal metrics
Usage
meal_metrics(data, mealtimes, before_win = 1, after_win = 3,
recovery_win = 1, interpolate = TRUE, adjust_mealtimes = TRUE, dt0 = NULL,
inter_gap = 45, tz = "", glucose_times = FALSE)Arguments
- data
DataFrame object with column names "id", "time", and "gl". Should only be data for 1 subject. In case multiple subject ids are detected, a warning is produced and only 1st subject is used.
- mealtimes
Either a vector of mealtimes, corresponding to data being from a single subject, OR a dataframe with at least 2 columns labeled id and mealtime. Optionally the mealtimes dataframe can include a column labeled meal, giving the meal type (helps to compensate for overlapping meals)
- before_win
integer specifying number of hours to extend window before meal
- after_win
integer specifying number of hours to extend window after meal
- recovery_win
interger specifying number of hours for recovery beyond after window
- interpolate
Boolean to indicate if CGM data should be interpolated or not. Default set to FALSE due to time intensive nature of interpolation. Parameters dt0, inter_gap, and tz will only be used if interpolate is set to TRUE.
- adjust_mealtimes
Boolean to indicate if function should attempt to align mealtimes with CGM data times. This is important if mealtimes and CGM data times are not exactly aligned, because the function will return NA's for mealtimes that don't match with a corresponding CGM time stamp.
- dt0
The time frequency for interpolation in minutes, the default will match the CGM meter's frequency (e.g. 5 min for Dexcom).
- inter_gap
The maximum allowable gap (in minutes) for interpolation. The values will not be interpolated between the glucose measurements that are more than inter_gap minutes apart. The default value is 45 min.
- tz
A character string specifying the time zone to be used. System-specific (see
as.POSIXct), but " " is the current time zone, and "GMT" is UTC (Universal Time, Coordinated). Invalid values are most commonly treated as UTC, on some platforms with a warning.- glucose_times
Boolean to indicate if underlying glucose and times should be returned - e.g. baseline glucose value used to calculate \(Delta G\). Intended for use in plotting function
Value
By default tibble object with 6 columns will be returned: id, time, meal, deltag, deltat, and basereco. If glucose_times = TRUE then 5 more columns are returned for baseline glucose (basegl), peak glucose (peakgl), recover glucose (recovergl), peak timestamp (peaktime), and recovery timestamp (recovertime)
Details
A tibble object is returned with three metrics calculated for each mealtime. The last three columns of the output correspond to the three metrics: deltag refers to \(\Delta G\), deltat is \(\Delta T\), and basereco is % Baseline recovery. If no meal column is given in the original data, one will be automatically generated with a unique number for each meal.
References
Service, F. John. (2013) Glucose Variability, Diabetes 62(5): 1398-1404, doi:10.2337/db12-1396
Examples
data(example_data_hall)
data(example_meals_hall)
meal_metrics(example_data_hall, example_meals_hall)
#> No mealtimes found for subject: 1636-69-001
#> No mealtimes found for subject: 1636-69-026
#> No mealtimes found for subject: 1636-69-032
#> No mealtimes found for subject: 1636-69-090
#> No mealtimes found for subject: 1636-69-091
#> No mealtimes found for subject: 1636-69-114
#> No mealtimes found for subject: 1636-70-1005
#> No mealtimes found for subject: 1636-70-1010
#> No mealtimes found for subject: 2133-015
#> No mealtimes found for subject: 2133-017
#> No mealtimes found for subject: 2133-019
#> No mealtimes found for subject: 2133-021
#> No mealtimes found for subject: 2133-024
#> No mealtimes found for subject: 2133-027
#> No mealtimes found for subject: 2133-035
#> No mealtimes found for subject: 2133-036
#> Warning: There was 1 warning in `dplyr::reframe()`.
#> ℹ In argument: `meal_metrics_single(...)`.
#> ℹ In group 9: `id = "2133-004"`.
#> Caused by warning in `meal_metrics_single()`:
#> ! Some meals don't match with CGM readings. Mealtimes returned with NA for metric values
#> # A tibble: 25 × 6
#> id time meal deltag deltat basereco
#> <chr> <dttm> <chr> <dbl> <dbl> <dbl>
#> 1 1636-69-001 NA NA NA NA NA
#> 2 1636-69-026 NA NA NA NA NA
#> 3 1636-69-032 NA NA NA NA NA
#> 4 1636-69-090 NA NA NA NA NA
#> 5 1636-69-091 NA NA NA NA NA
#> 6 1636-69-114 NA NA NA NA NA
#> 7 1636-70-1005 NA NA NA NA NA
#> 8 1636-70-1010 NA NA NA NA NA
#> 9 2133-004 2016-09-23 10:10:00 CF 1 87.8 80 0.362
#> 10 2133-004 2016-09-27 09:40:00 PB 1 NA NA NA
#> # ℹ 15 more rows