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.

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.

## References

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

## See also

## Author

Stef van Buuren 2020

## Examples

#> 0.5 1
#> -0.425 0.299

#> 0.5 1
#> -0.091 0.357

#> 0.5 1 2
#> 36.32 49.11 62.67

#> 0.5 1 2
#> 35.27 48.91 63.77