# y2p: Convert measurements into centiles In growthcharts/yzy: Translate Measurements, Z-Scores and Centiles with the RIF format

 y2p R Documentation

## Convert measurements into centiles

### Description

Converts measurements into age- or hgt-conditional centile scores using one or more external reference distributions.

### Usage

``````y2p(
y,
x,
refcode,
pkg = "centile",
verbose = FALSE,
dec = 3L,
rule = 1L,
scale = 100,
...
)
``````

### Arguments

 `y` A numerical vector with measurements'. `x` A vector containing `length(y)` values of the numerical covariate (typically decimal age or height) at which conversion is desired. A scalar `x` will be expanded to `length(y)`. `refcode` A character vector with `length(y)` elements, each of which is the name of a reference. Scalar `refcode` expands to `length(y)`. Alternatively, `refcode` may be an object of class `reference`, typically produced by `import_rif()`. If `NULL` the procedure returns `NA`'s. `pkg` The package containing the references in the `R/sysdata.dta` object. The package needs to be loaded. The default `pkg = "centile"` searches in the `centile` package. `verbose` Set to `TRUE` to turn on warnings `dec` A scalar value indicating the number of decimals used to round the value. The default is 3 decimals. `rule` an integer (of length 1 or 2) describing how interpolation is to take place outside the interval [`min(x)`, `max(x)`]. If `rule` is `1` then `NA`s are returned for such points and if it is `2`, the value at the closest data extreme is used. Use, e.g., `rule = 2:1`, if the left and right side extrapolation should differ. `tail_adjust` Logical. If `TRUE` the procedure applies the WHO method for tail adjustment under the LMS distribution. We do not recommend this. The default is `FALSE`. `scale` The maximum of the scale. The default (`100`) returns percentiles. Set `scale = 1` to obtain probabilities. `...` Not used.

### Value

A vector with `length(y)` elements containing centiles.

### Note

The type of reference distribution is defined by the `distribution` field of the `study` attribute in the reference. The function executes transformations specified by the `tx` and `ty` fields before calculating the Z-score.

Functions `y2p()` and `p2y()` functions are the inverse of each other.

### Author(s)

Stef van Buuren, 2021

### Examples

``````y <- c(50, 50, 60, 60, 4, 4, 4, 4)
x <- c(rep(0.1, 4), rep(0.1, 4))
refcode <- c(
rep(c("who_2006_hgt_male_", "who_2006_hgt_female_"), 2),
rep(c("who_2006_wgt_male_", "who_2006_wgt_female_"), 2)
)
y2p(y, x, refcode)
``````

growthcharts/yzy documentation built on May 4, 2024, 11:06 p.m.