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Convert z-scores/centiles to anthropometric measures using international growth standards

Source: R/conversion.R
zscore2value.Rd

Convert z-scores/centiles to anthropometric measures using international growth standards

Usage

zscore2value(z, x, sex = NULL, family, acronym)

centile2value(p, x, sex = NULL, family, acronym)

Arguments

z, p

Numeric vector of length one or more with centiles/z-scores to convert to values. For p, gigs will warn you if elements of p are not between 0 and 1. You can customise this behaviour using the GIGS package-level options.

x

Numeric vector of x values, which take on different units depending on the growth standard in use. To know which units to use, run report_units(family, acronym). Limits for each combination are as follows:

  • WHO Growth Standards (family = "who_gs")

    • Between 0 and 1856 days for "wfa", "bfa", "lhfa", and "hcfa".

    • Between 45 and 110 cm for "wfl".

    • Between 65 and 120 cm for "wfh".

    • Between 91 and 1856 days for "acfa", "ssfa", "tsfa".

  • INTERGROWTH-21st Fetal Standards (family = "ig_fet")

    • Between 98 and 280 days for "hcfga", "bpdfga", "acfga", "flfga", "ofdfga", and
      "tcdfga".

    • Between 154 and 280 days for "efwfga".

    • Between 112 and 294 days for "sfhfga".

    • Between 58 and 105 days for "crlfga".

    • Between 19 and 95 mm for "gafcrl".

    • Between 105 and 280 days for "gwgfga".

    • Between 168 and 280 days for "pifga", "rifga", and "sdrfga" (the INTERGROWTH-21st Fetal Doppler standards).

    • Between 12 and 55 mm for"tcdfga".

    • Between 105 and 252 days for "poffga", "sffga", "avfga", "pvfga", and "cmfga" (the INTERGROWTH-21st Fetal Brain Development standards).

    • Between 126 and 287 days for "hefwfga" (the INTERGROWTH-21st standard for Hadlock-based estimated fetal weight).

  • INTERGROWTH-21st Newborn Size Standards (family = "ig_nbs")

    • Between 168 and 300 days for "wfga", "lfga", "hcfga", and "wlrfga".

    • Between 266 and 280 days for "fmfga", "bfpfga", and "ffmfga".

  • Extended INTERGROWTH-21st Newborn Size Standards (family = "ig_nbs_ext")

    • Between 154 and 314 days for "wfga", "lfga", and "hcfga".

  • INTERGROWTH-21st Postnatal Growth Standards (family = "ig_png")

    • Between 27 and 64 weeks for "wfa", "lfa", and "hcfa".

    • Between 35 and 65 cm for "wfl".

By default, gigs will replace out-of-bounds elements in x with NA and warn you. It will also warn you about elements in x which are missing (NA) or undefined (NaN/Inf). You can customise this behaviour using the GIGS package-level options.

sex

Character vector of length one or more with sex(es), either "M" (male) or "F" (female). This argument should be left as NULL (the default) if family == "ig_fet". This argument is case-sensitive. By default, gigs will replace elements of sex which are not "M" or "F" with NA and warn you. You can customise this behaviour using the GIGS package-level options.

family

A single string denoting the family of growth standards in use. Must be one of "ig_fet", "ig_nbs", "ig_png", or "who_gs", or the function will throw an error. This argument is case-sensitive.

acronym

A single string denoting the specific growth standard in use. The allowed values of acronym depend on the value of family, and are listed in the documentation for the x argument. Incompatible family and acronym values will cause errors to be thrown. This argument is case-sensitive.

Value

Numeric vector of expected measurements with length equal to the longest input vector.

References

  • For the INTERGROWTH-21st Fetal standards see the gigs::ig_fet documentation

  • For the INTERGROWTH-21st Newborn Size standards see the gigs::ig_nbs documentation

  • For the INTERGROWTH-21st Postnatal Growth standards see the gigs::ig_png documentation

  • For the WHO Growth standards see the gigs::who_gs documentation

Examples

# Convert in the weight-for-age standard from the WHO Child Growth Standards
zscore2value(-2:2, 0, "M", family = "who_gs", acronym = "wfa")
#> [1] 2.459312 2.880651 3.346400 3.858619 4.419354

# Or obtain centiles...
centile2value(pnorm(-2:2), 0, "M", family = "who_gs", acronym = "wfa")
#> [1] 2.459312 2.880651 3.346400 3.858619 4.419354

# Inputs will be recycled if necessary
centile2value(3, 280, c("M", "F"), family = "ig_nbs", acronym = "wfga")
#> Warning: Input arguments have invalid values:
#> ℹ Argument `p`: All (1) elements were not between 0 and 1.
#> [1] NA NA