iglu (version 4.2.2)

sd_roc: Calculate the standard deviation of the rate of change

Description

The function sd_roc produces the standard deviation of the rate of change values in a tibble object.

Usage

sd_roc(data, timelag = 15, dt0 = NULL, inter_gap = 45, tz = "")

Value

A tibble object with two columns: subject id and standard deviation of the rate of change values for each subject.

Arguments

data

DataFrame object with column names "id", "time", and "gl".

timelag

Integer indicating the time period (# minutes) over which rate of change is calculated. Default is 15, e.g. rate of change is the change in glucose over the past 15 minutes divided by 15.

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.

Author

Elizabeth Chun, David Buchanan

Details

A tibble object with one row for each subject, a column for subject id and a column for the standard deviation of the rate of change.

When calculating rate of change, missing values will be linearly interpolated when close enough to non-missing values.

Calculated by taking the standard deviation of all the ROC values for each individual subject. NA rate of change values are omitted from the standard deviation calculation.

References

Clarke et al. (2009) Statistical Tools to Analyze Continuous Glucose Monitor Data, Diabetes Diabetes Technology and Therapeutics 11 S45-S54, tools:::Rd_expr_doi("10.1089/dia.2008.0138").

Examples

data(example_data_1_subject)
sd_roc(example_data_1_subject)
sd_roc(example_data_1_subject, timelag = 10)

data(example_data_5_subject)
sd_roc(example_data_5_subject)
sd_roc(example_data_5_subject, timelag = 10)