Returns the field_start and field_end dataset-level metadata keys from a
survey design object or a data frame.
Value
A named list of length 2, field_start then field_end, each a
Date of length 1. An unset key is as.Date(NA).
Details
Returns the two structured dates only. The prose field period has its own
extractor, extract_field_period(), and this function never derives one
from the other. An unset key is a normal state, reported as as.Date(NA);
this function never warns. A design object restored from a file written by
surveycore 1.1.0 or earlier reports both entries as as.Date(NA) rather
than failing.
See also
Other metadata:
classify_question_type(),
extract_data_name(),
extract_dataset_metadata(),
extract_field_period(),
extract_higher_is(),
extract_metadata(),
extract_missing_codes(),
extract_question_preface(),
extract_reverse_coded(),
extract_sata(),
extract_survey_name(),
extract_universe(),
extract_val_labels(),
extract_var_extra(),
extract_var_label(),
extract_var_note(),
extract_vendor(),
infer_question_prefaces(),
set_data_name(),
set_dataset_metadata(),
set_field_dates(),
set_field_period(),
set_higher_is(),
set_missing_codes(),
set_question_preface(),
set_reverse_coded(),
set_sata(),
set_survey_name(),
set_universe(),
set_val_labels(),
set_var_extra(),
set_var_label(),
set_var_note(),
set_vendor(),
survey_metadata(),
survey_weighting_history()
Examples
df <- data.frame(id = 1:5, y = c(2, 4, 3, 5, 1), w = rep(1, 5))
extract_field_dates(df)
#> $field_start
#> [1] NA
#>
#> $field_end
#> [1] NA
#>
df <- set_field_dates(df, "2026-02-10", "2026-03-04")
extract_field_dates(df)
#> $field_start
#> [1] "2026-02-10"
#>
#> $field_end
#> [1] "2026-03-04"
#>