# daz: D-score standard deviation score: DAZ In dscore: D-Score for Child Development

## Description

The `daz()` function calculated the "Development for Age Z-score". The DAZ represents a child's D-score after adjusting for age by an external age-conditional reference. The `zad()` is the inverse of `daz()`: Given age and the Z-score, it finds the raw D-score.

## Usage

 ```1 2 3``` ```daz(d, x = as.numeric(names(d)), reference = get_reference(), dec = 3) zad(z, x = as.numeric(names(z)), reference = get_reference(), dec = 2) ```

## Arguments

 `d` Vector of D-scores `x` Vector of ages (decimal age) `reference` A `data.frame` with the LMS reference values. The default uses the `get_reference()` function. This selects a subset of rows from the `builtin_references` using its default `pop` argument. `dec` The number of decimals (default `dec = 3`). `z` Vector of standard deviation scores (DAZ)

## Value

The `daz()` function return a named vector with Z-scores with `length(d)` elements

The `zad()` function returns a vector with D-scores with `length(z)` elements.

## Author(s)

Stef van Buuren 2020

## References

Cole TJ, Green PJ (1992). Smoothing reference centile curves: The LMS method and penalized likelihood. Statistics in Medicine, 11(10), 1305-1319.

`dscore()`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18``` ```# using gcdg-reference daz(d = c(35, 50), x = c(0.5, 1.0)) # using Dutch reference daz(d = c(35, 50), x = c(0.5, 1.0), reference = get_reference("dutch")) # population median at ages 0.5, 1 and 2 years, gcdg reference zad(z = rep(0, 3), x = c(0.5, 1, 2)) # population median at ages 0.5, 1 and 2 years, dutch reference zad(z = rep(0, 3), x = c(0.5, 1, 2), reference = get_reference("dutch")) # percentiles of D-score reference g <- expand.grid(age = seq(0.1, 2, 0.1), p = c(0.1, 0.5, 0.9)) d <- zad(z = qnorm(g\$p), x = g\$age) matplot( x = matrix(g\$age, ncol = 3), y = matrix(d, ncol = 3), type = "l", lty = 1, col = "blue", xlab = "Age (years)", ylab = "D-score" ) ```