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

Source: R/conversion.R
value2zscore.Rd

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

Usage

value2zscore(y, x, sex = NULL, family, acronym)

value2centile(y, x, sex = NULL, family, acronym)

Arguments

y

Numeric vector of length one or more with anthropometric measurement(s) to convert to centiles/z-scores. Units depend on which combination of family and acronym are in use, which you can check with report_units(). By default, GIGS will warn you if elements in y are missing (NA) or undefined (NaN/Inf), and replace the latter with NA. 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 z-scores/centiles with length equal to the longest input vector.

Note

Inputs other than acronym and family will be recycled by vctrs::vec_recycle_common(), and must adhere to the vctrs recycling rules.

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

See also

report_units() will tell you the units needed for y and x, for any combination of family and acronym.

Examples

# Convert in the weight-for-age standard from the WHO Child Growth Standards
value2zscore(3, 0, "M", family = "who_gs", acronym = "wfa")
#> [1] -0.7342639

# Or obtain centiles...
value2centile(3, 0, "M", family = "who_gs", acronym = "wfa")
#> [1] 0.231394

# Inputs will be recycled if necessary
value2centile(2.5, 280, c("M", "F"), family = "ig_nbs", acronym = "wfga")
#> [1] 0.01444696 0.02267229