Calculates the M-value of Schlichtkrull et al. (1965) for each subject in the data, where the M-value is the mean of the logarithmic transformation of the deviation from a reference value. Produces a tibble object with subject id and M-values.
Arguments
- data
DataFrame object with column names "id", "time", and "gl", or numeric vector of glucose values.
- r
A reference value corresponding to basal glycemia in normal subjects; default is 90 mg/dL.
Value
If a data.frame object is passed, then a tibble object with two columns: subject id and corresponding M-value is returned. If a vector of glucose values is passed, then a tibble object with just the M-value is returned. as.numeric() can be wrapped around the latter to output just a numeric value.
Details
A tibble object with 1 row for each subject, a column for subject id and a column for the M-values is returned. NA glucose values are omitted from the calculation of the M-value.
M-value is computed by averaging the transformed glucose values, where each transformed value is equal to \(|10 * log_10(glucose/r)|^3\), where r is the specified reference value.
References
Schlichtkrull J, Munck O, Jersild M. (1965) The M-value, an index of blood-sugar control in diabetics. Acta Medica Scandinavica 177 .95-102. doi:10.1111/j.0954-6820.1965.tb01810.x .
Examples
data(example_data_5_subject)
m_value(example_data_5_subject)
#> # A tibble: 5 × 2
#> id M_value
#> <fct> <dbl>
#> 1 Subject 1 7.02
#> 2 Subject 2 63.7
#> 3 Subject 3 19.9
#> 4 Subject 4 7.39
#> 5 Subject 5 34.8
m_value(example_data_5_subject, r = 100)
#> # A tibble: 5 × 2
#> id M_value
#> <fct> <dbl>
#> 1 Subject 1 4.10
#> 2 Subject 2 45.4
#> 3 Subject 3 12.8
#> 4 Subject 4 4.04
#> 5 Subject 5 24.0