mage: Calculate Mean Amplitude of Glycemic Excursions

In iglu: Interpreting Glucose Data from Continuous Glucose Monitors

Calculate Mean Amplitude of Glycemic Excursions

Description

The function calculates MAGE values and can optionally return a plot of the glucose trace.

Usage

mage(
  data,
  version = c("ma", "naive"),
  sd_multiplier = 1,
  short_ma = 5,
  long_ma = 32,
  type = c("auto", "plus", "minus"),
  plot = FALSE,
  dt0 = NULL,
  inter_gap = 45,
  tz = "",
  title = NA,
  xlab = NA,
  ylab = NA,
  show_ma = FALSE
)

Arguments

data	DataFrame object with column names "id", "time", and "gl" OR numeric vector of glucose values.
version	Either 'ma' or 'naive'. Chooses which version of the MAGE algorithm to use. 'ma' algorithm is more accurate, and is the default. Earlier versions of iglu package (<=2.0.0) used 'naive'.
sd_multiplier	A numeric value that can change the sd value used to determine size of glycemic excursions used in the calculation. This is the only parameter that can be specified for version = "naive", and it is ignored if version = "ma".
short_ma	Integer for period length of the short moving average. Must be positive and less than "long_ma", default value is 5. (Recommended <15)
long_ma	Integer for period length for the long moving average, default value is 32. (Recommended >20)
type	One of "plus", "minus", "auto" (Default: auto). Algorithm will either calculate MAGE+ (nadir to peak), MAGE- (peak to nadir), or automatically choose based on the first countable excursion.
plot	Boolean. Returns ggplot if TRUE.
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.
title	Title for the ggplot. Defaults to "Glucose Trace - Subject [ID]"
xlab	Label for x-axis of ggplot. Defaults to "Time"
ylab	Label for y-axis of ggplot. Defaults to "Glucose Level"
show_ma	Whether to show the moving average lines on the plot or not

Details

If version 'ma' is selected, the function computationally emulates the manual method for calculating the mean amplitude of glycemic excursions (MAGE) first suggested in "Mean Amplitude of Glycemic Excursions, a Measure of Diabetic Instability", (Service, 1970). For this version, glucose values will be interpolated over a uniform time grid prior to calculation.

'ma' is a more accurate algorithm that uses the crosses of a short and long moving average to identify intervals where a peak/nadir might exist. Then, the height from one peak/nadir to the next nadir/peak is calculated from the *original* (not moving average) glucose values.

'naive' algorithm calculates MAGE by taking the mean of absolute glucose differences (between each value and the mean) that are greater than the standard deviation. A multiplier can be added to the standard deviation using the sd_multiplier argument.

Value

A tibble object with two columns: the subject id and corresponding MAGE value. If a vector of glucose values is passed, then a tibble object with just the MAGE value is returned. In version = "ma", if plot = TRUE, a list of ggplots will be returned with one plot per subject.

References

Service et al. (1970) Mean amplitude of glycemic excursions, a measure of diabetic instability Diabetes 19 .644-655, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.2337/diab.19.9.644")}.

Examples

data(example_data_5_subject)
mage(example_data_5_subject, version = 'ma')

iglu documentation built on Oct. 20, 2023, 5:07 p.m.