The get_reference() function selects the D-score reference
distribution.
get_reference(
population = NULL,
key = NULL,
references = dscore::builtin_references,
verbose = FALSE,
...
)String. The name of the reference population to calculate
DAZ.
Use with(builtin_references, table(key, population)) to see which
built-in references are available for key - population combinations.
If not specified, the function set the default population as
builtin_keys$base_population[key == builtin_keys$key].
String. They key identifies 1) the difficulty estimates
pertaining to a particular Rasch model, and 2) the prior mean and standard
deviation of the prior distribution for calculating the D-score.
The default key NULL sets key = "gsed2406".
View builtin_keys for an overview of the available keys.
A data.frame with the same structure as builtin_references.
The default is to use builtin_references.
Logical. Print settings.
Used to test whether the call contained the deprecated argument
references.
A data.frame with the LMS reference values.
No references for population "gsed" exist.
The function will silently rewrite population = "gsed"
into to the population = "gsed".
The "dutch" reference was published in Van Buuren (2014)
The "gcdg" was calculated from 15 cohorts with direct
observations (Weber, 2019).
The "phase1" references were calculated from the GSED Phase 1 validation
data (GSED-BGD, GSED-PAK, GSED-TZA) cover age range 2w-3.5 years. The
age range 3.5-5 yrs is linearly extrapolated and are only indicative.
(Van Buuren et al, 2025)
The "preliminary_standards" references were calculated from the GSED
Phase 1 validation using a subset of children with healthy development.
(Van Buuren et al, 2025)
The "who_descriptive" references were calculated from the GSED
Phase 1 + 2 (Seven countries) validation study using the "gsed2510" key.
It is a descriptive reference, i.e., no selection of children growing
up in healthy environments was made. (In preparation for publication).
Van Buuren S (2014). Growth charts of human development. Stat Methods Med Res, 23(4), 346-368.
Weber AM, Rubio-Codina M, Walker SP, van Buuren S, Eekhout I, Grantham-McGregor S, Caridad Araujo M, Chang SM, Fernald LCH, Hamadani JD, Hanlon A, Karam SM, Lozoff B, Ratsifandrihamanana L, Richter L, Black MM (2019). The D-score: a metric for interpreting the early development of infants and toddlers across global settings. BMJ Global Health, BMJ Global Health 4: e001724. https://gh.bmj.com/content/bmjgh/4/6/e001724.full.pdf.
van Buuren S, Eekhout I, McCray G, Lancaster GA, Waldman MR, McCoy DC, Gladstone M, Cavallera, V, Dua T, Black MM, GSED Team (2025). Enhancing comparability in early child development assessment with the D-score. International Journal of Behavioral Development, 49(4), 348-364, https://doi.org/10.1177/01650254241294033
# see key-population combinations of builtin_references
table(builtin_references$key, builtin_references$population)
#>
#> dutch gcdg phase1 preliminary_standards who_descriptive
#> 293_0 0 0 186 0 0
#> dutch 144 0 0 0 0
#> gcdg 0 121 0 0 0
#> gsed1912 0 121 0 0 0
#> gsed2212 185 0 186 0 0
#> gsed2406 185 0 186 186 0
#> gsed2510 185 0 0 186 188
# get the default reference
reftab <- get_reference()
head(reftab, 2)
#> population key distribution age mu sigma nu
#> 1501 preliminary_standards gsed2510 BCT 0.0000 11.46 0.2075 1.42
#> 1502 preliminary_standards gsed2510 BCT 0.0383 13.18 0.2075 1.42
#> tau P3 P10 P25 P50 P75 P90 P97
#> 1501 34.189 6.333258 8.150177 9.791339 11.46264 13.03831 14.41592 15.76832
#> 1502 34.189 7.283800 9.373415 11.260895 13.18304 14.99519 16.57957 18.13494
#> SDM2 SDM1 SD0 SDP1 SDP2
#> 1501 5.941355 8.93160 11.46264 13.77963 16.03876
#> 1502 6.833076 10.27212 13.18304 15.84778 18.44597
# get the default reference for the key "gsed2212"
reftab <- get_reference(key = "gsed2212", verbose = TRUE)
#> key: gsed2212
#> population: phase1
# get dutch reference for default key
reftab <- get_reference(population = "dutch", verbose = TRUE)
#> key: gsed2510
#> population: dutch
# loading a non-existing reference yield fallback to default
reftab <- get_reference(population = "france", verbose = TRUE)
#> key: gsed2510
#> population: france
#> Warning: Reference 'france' for key 'gsed2510' not found. Fallback: 'preliminary_standards' for key 'gsed2406'.
# if user specifies a builtin population (e.g. who_descriptive) and the key
# is not found, then it returns the specified reference for its most recent key
reftab <- get_reference(key = "none", population = "preliminary_standards", verbose = TRUE)
#> key: none
#> population: preliminary_standards
#> Using key: gsed2510
nrow(reftab)
#> [1] 186