The get_reference() function selects the D-score reference distribution.

get_reference(
  population = NULL,
  key = NULL,
  references = dscore::builtin_references,
  verbose = FALSE,
  ...
)

Arguments

population

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].

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.

references

A data.frame with the same structure as builtin_references. The default is to use builtin_references.

verbose

Logical. Print settings.

...

Used to test whether the call contained the deprecated argument references.

Value

A data.frame with the LMS reference values.

Note

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).

References

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

Examples

# 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