Read an Arrow multi-file dataset and create sf object
read_sf_dataset(dataset, find_geom = FALSE)
Arguments
| dataset | a |
|---|---|
| find_geom | logical. Only needed when returning a subset of columns.
Should all available geometry columns be selected and added to to the
dataset query without being named? Default is |
Value
object of class sf
Details
This function is primarily for use after opening a dataset with
arrow::open_dataset. Users can then query the arrow Dataset
using dplyr methods such as filter or
select. Passing the resulting query to this function
will parse the datasets and create an sf object. The function
expects consistent geographic metadata to be stored with the dataset in
order to create sf objects.
See also
Examples
# read spatial object nc <- sf::st_read(system.file("shape/nc.shp", package="sf"), quiet = TRUE) # create random grouping nc$group <- sample(1:3, nrow(nc), replace = TRUE) # use dplyr to group the dataset. %>% also allowed nc_g <- dplyr::group_by(nc, group) # write out to parquet datasets tf <- tempfile() # create temporary location on.exit(unlink(tf)) # partitioning determined by dplyr 'group_vars' write_sf_dataset(nc_g, path = tf)#> Warning: This is an initial implementation of Parquet/Feather file support and #> geo metadata. This is tracking version 0.1.0 of the metadata #> (https://github.com/geopandas/geo-arrow-spec). This metadata #> specification may change and does not yet make stability promises. We #> do not yet recommend using this in a production setting unless you are #> able to rewrite your Parquet/Feather files.#> [1] "group=1/part-0.parquet" "group=2/part-1.parquet" "group=3/part-2.parquet"# open parquet files from dataset ds <- arrow::open_dataset(tf) # create a query. %>% also allowed q <- dplyr::filter(ds, group == 1) # read the dataset (piping syntax also works) nc_d <- read_sf_dataset(dataset = q) nc_d#> Simple feature collection with 33 features and 15 fields #> Geometry type: MULTIPOLYGON #> Dimension: XY #> Bounding box: xmin: -83.98855 ymin: 33.94867 xmax: -75.45698 ymax: 36.58965 #> Geodetic CRS: NAD27 #> First 10 features: #> AREA PERIMETER CNTY_ CNTY_ID NAME FIPS FIPSNO CRESS_ID BIR74 SID74 #> 1 0.114 1.442 1825 1825 Ashe 37009 37009 5 1091 1 #> 2 0.070 2.968 1831 1831 Currituck 37053 37053 27 508 1 #> 3 0.124 1.428 1837 1837 Stokes 37169 37169 85 1612 1 #> 4 0.114 1.352 1838 1838 Caswell 37033 37033 17 1035 2 #> 5 0.153 1.616 1839 1839 Rockingham 37157 37157 79 4449 16 #> 6 0.072 1.085 1842 1842 Vance 37181 37181 91 2180 4 #> 7 0.064 1.213 1892 1892 Avery 37011 37011 6 781 0 #> 8 0.086 1.267 1893 1893 Yadkin 37197 37197 99 1269 1 #> 9 0.128 1.554 1897 1897 Franklin 37069 37069 35 1399 2 #> 10 0.142 1.640 1913 1913 Nash 37127 37127 64 4021 8 #> NWBIR74 BIR79 SID79 NWBIR79 group geometry #> 1 10 1364 0 19 1 MULTIPOLYGON (((-81.47276 3... #> 2 123 830 2 145 1 MULTIPOLYGON (((-76.00897 3... #> 3 160 2038 5 176 1 MULTIPOLYGON (((-80.02567 3... #> 4 550 1253 2 597 1 MULTIPOLYGON (((-79.53051 3... #> 5 1243 5386 5 1369 1 MULTIPOLYGON (((-79.53051 3... #> 6 1179 2753 6 1492 1 MULTIPOLYGON (((-78.49252 3... #> 7 4 977 0 5 1 MULTIPOLYGON (((-81.94135 3... #> 8 65 1568 1 76 1 MULTIPOLYGON (((-80.49554 3... #> 9 736 1863 0 950 1 MULTIPOLYGON (((-78.25455 3... #> 10 1851 5189 7 2274 1 MULTIPOLYGON (((-78.18693 3...
