# Head Circumference for Age - Pediatric Growth Standard

Source:`R/head_circumference_for_age.R`

`head_circumference_for_age.Rd`

Head Circumference for age quantile, distribution, and zscore function based on LMS data from the CDC and WHO.

## Arguments

- q
a vector of quantiles

- male
integer value, 1 = male, 0 = female

- age
numeric age, in months

- source
a character string denoting the data source providing the parameters needed for the estimate. Valid values are "CDC" and "WHO". This can be set explicitly, or by using the

`pedbp_pgs_source`

option.- ...
pass through

- p
a vector of probabilities

## Value

`p_`

method return values from the estimated distribution function.

`q_`

methods return values from the estimated quantile function.

`z_`

methods return standard scores.

## Notes

CDC Recommends using WHO growth charts for infants and children ages 0 to 2 years of age in the U.S. and CDC growth charts to monitor growth for children age 2 years and older in the U.S.

## References

https://www.cdc.gov/growthcharts/percentile_data_files.htm, https://www.who.int/tools/child-growth-standards/standards

## Examples

```
# The median head circumfernce for a two-year-old female:
q_head_circumference_for_age(p = 0.5, male = 0, age = 24, source = "CDC")
#> [1] 47.40516
# Find the percentile for a 13 month old male with a head circumfernce of 46 cm:
p <- p_head_circumference_for_age(q = 46, male = 1, age = 13, source = "CDC")
p
#> [1] 0.3482039
# the standard score is the quantile from a standard normal
z_head_circumference_for_age(q = 46, male = 1, age = 13, source = "CDC")
#> [1] -0.390174
qnorm(p)
#> [1] -0.390174
# WHO not yet implimented
tryCatch(q_head_circumference_for_age(0.5, male = 0, age = 24, source = "WHO"),
error = function(e) e)
#> [1] 47.1799
```