The variables in an NHANES III file: names, labels and column positions

Parses the SAS program that ships with each NHANES III file. This is the stage where you can stop and choose which columns to read: the exam file has more than 2,000 and the adult questionnaire more than 1,200, and reading a handful by position is fast while reading them all is not. Only the small .sas file is needed, not the large .dat.

Usage

nhanes3_layout(
  file,
  pattern = NULL,
  ignore.case = TRUE,
  sas_file = NULL,
  refresh = FALSE
)

Arguments

file: A file name from nhanes3_files(), or the path to a .sas program.
pattern: Optional regular expression; keep the variables whose name or label matches it, for example "height|weight|waist".
ignore.case: Match pattern without regard to case (default TRUE).
sas_file: Path to the .sas program, if you already have it; otherwise the cached copy is used, downloaded on first use.
refresh: Download the .sas file again.

Value

A data frame of class nhanes3_layout with one row per variable: var, label (NA if the SAS program gives none), start, end, width (the number of characters in the field) and type ("numeric" or "character"). The record length is checked against the layout and stored in attr(, "lrecl").

Details

Labels are the short descriptions from the SAS program (for example "How tall are you without shoes - inches"). Value labels and the missing-value codes of each variable are in the codebook PDF, and a variable's own special codes (for example 666 for "varies") are not the same as the all-8s/all-9s codes that nhanes3_read() can recode; check the codebook before recoding (see the nhanes-iii vignette).

Examples

if (FALSE) { # \dontrun{
nhanes3_layout("adult", pattern = "tall|weigh")   # heights and weights people reported
nhanes3_layout("exam", pattern = "^BMP")          # the body-measure variables
} # }