Description Details Author(s) References See Also Examples

Fits non-crossing regression quantiles as a function of linear covariates and smooth terms via B-splines with difference penalties. Automatic smoothness estimation for several spline terms is allowed.

Package: | quantregGrowth |

Type: | Package |

Version: | 1.1-0 |

Date: | 2021-03-24 |

License: | GPL |

Package quantregGrowth allows estimation of growth charts via quantile regression. Given a set of percentiles, `gcrq`

estimates non-crossing quantile curves as a flexible function of quantitative covariates (typically age), and possibly
additional linear terms. To ensure flexibility, B-splines with a difference *L1* penalty are employed to estimate nonparametrically
the curves; additionally monotonicity and concavity constraints may be also set. Multiple smooth terms are allowed and the amount of smoothness for each term is
efficiently included in the model fitting algorithm, see Muggeo et al. (2020). `plot.gcrq`

displays the fitted lines along with observations and poitwise confidence intervals.

Vito M.R. Muggeo

Maintainer: Vito M.R. Muggeo <vito.muggeo@unipa.it>

Muggeo VMR, Torretta F, Eilers PHC, Sciandra M, Attanasio M (2020).
Multiple smoothing parameters selection in additive regression quantiles,
*Statistical Modelling*, to appear.

Muggeo VMR, Sciandra M, Tomasello A, Calvo S (2013).
Estimating growth charts via nonparametric quantile
regression: a practical framework with application
in ecology, *Environ Ecol Stat*, **20**, 519-531.

Muggeo VMR (2018). Using the R package quantregGrowth: some examples.

https://www.researchgate.net/publication/323573492

Some references on growth charts (the first two papers employ the so-called LMS method)

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

Rigby RA, Stasinopoulos DM (2004) Smooth centile curves for skew and kurtotic data modelled using the
Box-Cox power exponential distribution. *Statistics in Medicine* **23**, 3053-3076.

Wei Y, Pere A, Koenker R, He X (2006) Quantile regression methods for reference growth charts.
*Statistics in Medicine* **25**, 1369-1382.

Some references on regression quantiles

Koenker R (2005) Quantile regression. Cambridge University Press, Cambridge.

Cade BS, Noon BR (2003) A gentle introduction to quantile regression for ecologists. *Front Ecol Environ*
**1**, 412-420.

1 | ```
#see ?gcrq for some examples
``` |

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