Subset one or more surveys by retaining a specified set of variables. Subsetting can be performed either on surveys already loaded in memory or directly from survey files on disk.
If a crosswalk table is supplied, variables are selected based on the variables listed for each survey in the crosswalk, and variable names can optionally be harmonized using `var_name_target`.
This function replaces the deprecated helpers [subset_waves()] and [subset_save_surveys()].
Usage
subset_surveys(
survey_list,
survey_paths = NULL,
rowid = "rowid",
subset_name = "subset",
subset_vars = NULL,
crosswalk_table = NULL,
import_path = NULL,
export_path = NULL
)
subset_waves(waves, subset_vars = NULL)
subset_save_surveys(
crosswalk_table,
subset_name = "subset",
survey_list = NULL,
subset_vars = NULL,
survey_paths = NULL,
import_path = NULL,
export_path = NULL
)Arguments
- survey_list
A list of survey objects created by [read_surveys()]. If `NULL`, surveys are read from disk.
- survey_paths
A character vector of full file paths to survey files. Used when `survey_list` is `NULL`.
- rowid
Name of the unique observation identifier column. Defaults to `"rowid"`.
- subset_name
Character string appended to filenames of subsetted surveys. Defaults to `"subset"`.
- subset_vars
Character vector of variable names to retain. If `NULL`, all variables are retained.
- crosswalk_table
Optional crosswalk table created with [crosswalk_table_create()]. If supplied, variables are selected per survey based on `var_name_orig`, and variable names may be harmonized using `var_name_target`.
- import_path
Optional directory containing survey files. Used to resolve filenames when subsetting from disk.
- export_path
Optional directory where subsetted surveys are saved as `.rds` files. If `NULL`, surveys are returned in memory.
- waves
A list of surveys imported with [read_surveys()].
Value
Either: * a list of subsetted survey objects (if `export_path = NULL`), or * a character vector of filenames written to `export_path`.
Details
The function supports multiple workflows:
* **In-memory subsetting** using `survey_list` * **File-based subsetting** using `survey_paths` or `import_path` * **Crosswalk-driven subsetting**, where variables are selected per survey using a crosswalk table created by [crosswalk_table_create()]
If `export_path` is provided, subsetted surveys are written to disk as `.rds` files. Otherwise, subsetted surveys are returned in memory.
Examples
examples_dir <- system.file("examples", package = "retroharmonize")
survey_files <- dir(examples_dir, pattern = "\\.rds$")
surveys <- read_surveys(
file.path(examples_dir, survey_files),
export_path = NULL
)
subset_surveys(
survey_list = surveys,
subset_vars = c("rowid", "isocntry", "qa10_1", "qa14_1"),
subset_name = "example_subset"
)
#> [[1]]
#> Unknown (2026): Untitled Dataset [dataset]
#> rowid isocntry qa10_1
#> <chr> <chr> <dbl+lbl>
#> 1 ZA5913_1 NL 2 [Tend not to trust]
#> 2 ZA5913_2 NL 2 [Tend not to trust]
#> 3 ZA5913_3 NL 3 (NA) [DK]
#> 4 ZA5913_4 NL 1 [Tend to trust]
#> 5 ZA5913_5 NL 1 [Tend to trust]
#> 6 ZA5913_6 NL 1 [Tend to trust]
#> 7 ZA5913_7 NL 1 [Tend to trust]
#> 8 ZA5913_8 NL 1 [Tend to trust]
#> 9 ZA5913_9 NL 2 [Tend not to trust]
#> 10 ZA5913_10 NL 2 [Tend not to trust]
#> # ℹ 25 more rows
#>
#> [[2]]
#> Unknown (2026): Untitled Dataset [dataset]
#> rowid isocntry qa14_1
#> <chr> <chr> <dbl+lbl>
#> 1 ZA6863_1 NL 3 [DK]
#> 2 ZA6863_2 NL 1 [Tend to trust]
#> 3 ZA6863_3 NL 3 [DK]
#> 4 ZA6863_4 NL 1 [Tend to trust]
#> 5 ZA6863_5 NL 1 [Tend to trust]
#> 6 ZA6863_6 NL 2 [Tend not to trust]
#> 7 ZA6863_7 NL 1 [Tend to trust]
#> 8 ZA6863_8 NL 3 [DK]
#> 9 ZA6863_9 NL 1 [Tend to trust]
#> 10 ZA6863_10 NL 1 [Tend to trust]
#> # ℹ 40 more rows
#>
#> [[3]]
#> Unknown (2026): Untitled Dataset [dataset]
#> rowid isocntry qa14_1
#> <chr> <chr> <dbl+lbl>
#> 1 ZA7576_1 ES 2 [Tend not to trust]
#> 2 ZA7576_2 NL 1 [Tend to trust]
#> 3 ZA7576_3 NL 1 [Tend to trust]
#> 4 ZA7576_4 NL 2 [Tend not to trust]
#> 5 ZA7576_5 NL 1 [Tend to trust]
#> 6 ZA7576_6 NL 1 [Tend to trust]
#> 7 ZA7576_7 NL 1 [Tend to trust]
#> 8 ZA7576_8 NL 3 [DK]
#> 9 ZA7576_9 NL 2 [Tend not to trust]
#> 10 ZA7576_10 NL 2 [Tend not to trust]
#> # ℹ 35 more rows
#>