Read features fields (attributes), optionally after SQL execution.
vapour_read_fields(
dsource,
layer = 0L,
sql = "",
limit_n = NULL,
skip_n = 0,
extent = NA
)
vapour_read_attributes(
dsource,
layer = 0L,
sql = "",
limit_n = NULL,
skip_n = 0,
extent = NA
)data source name (path to file, connection string, URL)
integer of layer to work with, defaults to the first (0) or the name of the layer
if not empty this is executed against the data source (layer will be ignored)
an arbitrary limit to the number of features scanned
an arbitrary number of features to skip
apply an arbitrary extent, only when 'sql' used (must be 'ex = c(xmin, xmax, ymin, ymax)' but sp bbox, sf bbox, and raster extent also accepted)
list of vectors one for each field in the source, each will be the same length which will depend on the values of 'skip_n', 'limit_n', 'sql', and the available records in the source. The types will be raw, numeric, integer, character, logical depending on the available mapping to the types in the source for the data there to R's native vectors.
Internal types are not fully supported, there are straightforward conversions for numeric, integer (32-bit) and string types. Date, Time, DateTime are returned as character, and Integer64 is returned as numeric.
file <- "list_locality_postcode_meander_valley.tab"
mvfile <- system.file(file.path("extdata/tab", file), package="vapour")
att <- vapour_read_fields(mvfile)
str(att)
#> List of 11
#> $ LOCAL_ID : num [1:58] 1e+05 1e+05 1e+05 1e+05 1e+05 ...
#> $ NAME : chr [1:58] "Caveside" "Weegena" "Kimberley" "Parkham" ...
#> $ POSTCODE : int [1:58] 7304 7304 7304 7304 7275 7277 7250 7304 7304 7304 ...
#> $ PLAN_REF : chr [1:58] "CPR5322" "CPR5327" "CPR5361" "CPR5327" ...
#> $ GAZ_DATE : Date[1:58], format: "2624775-05-26" "2624775-05-26" ...
#> $ NOM_REG_NO: chr [1:58] "947L" "1300M" "1063T" "1179Y" ...
#> $ UFI : chr [1:58] "{4a5db4da-ca19-41a0-8dd4-c28a14bbee18}" "{253b676e-2791-469c-ac5e-9cb3a95cc158}" "{75f60a99-4c58-4d3e-911d-bbaa9a04164c}" "{b008d456-4e80-4237-80f6-a26c03817e3c}" ...
#> $ CREATED_ON: chr [1:58] "2016-03-04 10:42:37" "2015-06-19 13:46:50" "2016-09-16 10:54:56" "2014-06-06 16:50:22" ...
#> $ LIST_GUID : chr [1:58] "{839edd46-01a7-4a45-9d97-499962fa952b}" "{de35ebd4-0ac0-4299-947d-87d07c69426a}" "{73ced9ad-ee9a-41d5-a5bc-c95c4ab948d9}" "{37f17d1f-d2a0-4b78-ba0d-e5f62f216658}" ...
#> $ SHAPE_AREA: num [1:58] -9999 -9999 -9999 -9999 -9999 ...
#> $ SHAPE_LEN : num [1:58] 39786 31588 35693 67615 70141 ...
sq <- "SELECT * FROM list_locality_postcode_meander_valley WHERE FID < 5"
(att <- vapour_read_fields(mvfile, sql = sq))
#> $LOCAL_ID
#> [1] 100422 100366 100337 100308
#>
#> $NAME
#> [1] "Caveside" "Weegena" "Kimberley" "Parkham"
#>
#> $POSTCODE
#> [1] 7304 7304 7304 7304
#>
#> $PLAN_REF
#> [1] "CPR5322" "CPR5327" "CPR5361" "CPR5327"
#>
#> $GAZ_DATE
#> [1] "2624775-05-26" "2624775-05-26" "2638022-06-27" "2624775-05-26"
#>
#> $NOM_REG_NO
#> [1] "947L" "1300M" "1063T" "1179Y"
#>
#> $UFI
#> [1] "{4a5db4da-ca19-41a0-8dd4-c28a14bbee18}"
#> [2] "{253b676e-2791-469c-ac5e-9cb3a95cc158}"
#> [3] "{75f60a99-4c58-4d3e-911d-bbaa9a04164c}"
#> [4] "{b008d456-4e80-4237-80f6-a26c03817e3c}"
#>
#> $CREATED_ON
#> [1] "2016-03-04 10:42:37" "2015-06-19 13:46:50" "2016-09-16 10:54:56"
#> [4] "2014-06-06 16:50:22"
#>
#> $LIST_GUID
#> [1] "{839edd46-01a7-4a45-9d97-499962fa952b}"
#> [2] "{de35ebd4-0ac0-4299-947d-87d07c69426a}"
#> [3] "{73ced9ad-ee9a-41d5-a5bc-c95c4ab948d9}"
#> [4] "{37f17d1f-d2a0-4b78-ba0d-e5f62f216658}"
#>
#> $SHAPE_AREA
#> [1] -9999 -9999 -9999 -9999
#>
#> $SHAPE_LEN
#> [1] 39785.88 31587.54 35693.32 67614.51
#>
pfile <- "list_locality_postcode_meander_valley.tab"
dsource <- system.file(file.path("extdata/tab", pfile), package="vapour")
SQL <- "SELECT NAME FROM list_locality_postcode_meander_valley WHERE POSTCODE < 7300"
vapour_read_fields(dsource, sql = SQL)
#> $NAME
#> [1] "Frankford" "Bridgenorth" "Summerhill"
#> [4] "Carrick" "Rosevale" "Selbourne"
#> [7] "Blackstone Heights" "Lake St Clair" "Hagley"
#> [10] "Quamby Bend" "Trevallyn" "Westwood"
#> [13] "Riverside" "Hadspen" "Travellers Rest"
#> [16] "Prospect Vale"
#>