# Columnar Query Engine for Larger-than-RAM Data

## Documentation for package ‘vectra’ version 0.9.8

- DESCRIPTION file.
- User guides, package vignettes and other documentation.
- Package NEWS.

## Help Pages

A B C D E F G H I L M O P R S T U V W Z

## -- A --

across | Apply a function across multiple columns
anti_join | Join two vectra tables
append_vtr | Append rows to an existing .vtr file
arrange | Sort rows by column values
as_embedding | Encode vectors as an embedding column

## -- B --

bind_cols | Bind rows or columns from multiple vectra tables
bind_rows | Bind rows or columns from multiple vectra tables
block_fuzzy_lookup | Fuzzy-match query keys against a materialized block
block_lookup | Probe a materialized block by column value

## -- C --

chunk_feeder | Turn a query into a resettable chunk generator
collect | Execute a lazy query and return a data.frame
collect_chunked | Fold a function over a query, one batch at a time
collect_chunked.default | Fold a function over a query, one batch at a time
collect_chunked.vectra_node | Fold a function over a query, one batch at a time
collect_chunked.vectra_partition | Fold a function over a query, one batch at a time
collect_sf | Materialize a spatial query as an sf object
contours | Extract contour iso-lines from a streamed raster
cosine | Embedding distance functions
count | Count observations by group
create_index | Create a hash index on a .vtr file column
cross_join | Cross join two vectra tables

## -- D --

delete_vtr | Logically delete rows from a .vtr file
desc | Mark a column for descending sort order
diff_vtr | Compute the logical diff between two .vtr files
distinct | Keep distinct/unique rows
dot | Embedding distance functions

## -- E --

embedding_distance | Embedding distance functions
explain | Print the execution plan for a vectra query

## -- F --

filter | Filter rows of a vectra query
floor_time | Floor a datetime column to a calendar grid
focal | Moving-window (focal) statistics over a streamed raster
full_join | Join two vectra tables
fuzzy_join | Fuzzy join two vectra tables by string distance

## -- G --

geom_expressions | Geometry functions inside mutate(), filter(), and summarise()
glimpse | Get a glimpse of a vectra table
grid | Define a uniform grid for a partitioned spatial join
group_by | Group a vectra query by columns
group_map | Apply a function to each shard of a partition
group_map.vectra_partition | Apply a function to each shard of a partition
group_modify | Apply a function to each shard of a partition
group_modify.vectra_partition | Apply a function to each shard of a partition

## -- H --

has_index | Check if a hash index exists for a .vtr column
head.vectra_node | Limit results to first n rows

## -- I --

inner_join | Join two vectra tables
interval_join | Interval (range overlap) join of two vectra tables

## -- L --

l2 | Embedding distance functions
left_join | Join two vectra tables
link | Define a link between a fact table and a dimension table
lookup | Look up columns from linked dimension tables

## -- M --

mask | Mask a streamed raster to a polygon layer
materialize | Materialize a vectra node into a reusable in-memory block
mosaic | Merge aligned rasters onto a common grid
mutate | Add or transform columns

## -- O --

offload | Spill a query to disk and stream it back (the offload functor)

## -- P --

polygonize | Vectorise a raster into polygons
print.vectra_node | Print a vectra query node
proximity | Euclidean distance to the nearest feature (proximity)
pull | Extract a single column as a vector

## -- R --

rasterize | Rasterize a streamed point layer onto a fixed grid
rast_calc | Cellwise calculation over aligned rasters (map algebra)
reframe | Summarise with variable-length output per group
relocate | Relocate columns
rename | Rename columns
resample | Resample a time series to a calendar grid
right_join | Join two vectra tables
rolling | Time-based rolling aggregates
roll_max | Time-based rolling aggregates
roll_mean | Time-based rolling aggregates
roll_min | Time-based rolling aggregates
roll_n | Time-based rolling aggregates
roll_sum | Time-based rolling aggregates

## -- S --

select | Select columns from a vectra query
semi_join | Join two vectra tables
slice | Select rows by position
slice_head | Select first or last rows
slice_max | Select first or last rows
slice_min | Select first or last rows
slice_tail | Select first or last rows
spatial_centerline | Trace the centerline (medial axis) of streamed polygons
spatial_clip | Clip or erase a streamed layer against a resident mask
spatial_construct | Build a set-wise geometry construction, optionally per group
spatial_dissolve | Dissolve geometries by group
spatial_eliminate | Merge sliver polygons into a neighbour
spatial_explode | Explode multipart geometries into single-part features
spatial_filter | Keep streamed rows by their spatial relation to a resident layer
spatial_join | Spatial join a streamed query against a resident sf object
spatial_knn | k nearest neighbours of a streamed layer, with distances
spatial_line_merge | Merge contiguous line segments into maximal lines
spatial_locate | Locate streamed points along a resident line layer
spatial_map | Stream a query through an sf transform
spatial_network | Build a routable network graph from a line layer
spatial_overlay | Self-overlay a polygon layer into disjoint pieces (QGIS-style Union)
spatial_polygonize | Build polygonal faces from a line network
spatial_route | Shortest paths and origin-destination costs over a network
spatial_service_area | Service areas and isochrones over a network
spatial_simplify | Simplify a polygon coverage without tearing shared edges
spatial_smooth | Smooth streamed line and polygon geometry
spatial_snap | Snap a streamed layer toward a resident reference layer
spatial_snap_grid | Snap a streamed layer's coordinates to a fixed grid
spatial_split | Split a streamed layer by a resident blade, or return its crossing points
spatial_topology | Build the shared-edge topology of a polygon coverage
st_write.vectra_node | Stream a vectra node's geometry to a vector file
summarise | Summarise grouped data
summarize | Summarise grouped data

## -- T --

tally | Count observations by group
tbl | Create a lazy table reference from a .vtr file
tbl_csv | Create a lazy table reference from a CSV file
tbl_sqlite | Create a lazy table reference from a SQLite database
tbl_tiff | Create a lazy table reference from a GeoTIFF raster
tbl_xlsx | Create a lazy table reference from an Excel (.xlsx) file
terrain | Terrain derivatives from a streamed elevation raster
tiff_band_names | Read per-band names from a GeoTIFF
tiff_crs | Read CRS metadata from a GeoTIFF
tiff_extract_points | Extract raster values at point coordinates
tiff_metadata | Read GDAL_METADATA from a GeoTIFF
transmute | Keep only columns from mutate expressions

## -- U --

ungroup | Remove grouping from a vectra query

## -- V --

vec_build_overviews | Build overview pyramids for a .vec raster
vec_close_raster | Close a .vec raster handle
vec_extract_points | Extract band values at (x, y) points from a .vec raster
vec_open_raster | Open a .vec raster
vec_raster_layout | Tile layout of an open .vec raster
vec_raster_times | Distinct time stamps stored in a .vec time cube
vec_read_pixel_series | Read the full time series at a single pixel from a .vec time cube
vec_read_time_slice | Read a single time slice from a .vec time cube
vec_read_window | Read a window of pixels from a .vec raster
vec_to_tiff | Export a .vec raster to GeoTIFF
vec_write_raster | Write a raster matrix or 3D array to a .vec raster file
vec_write_time_cube | Write a 4D time-cube raster to .vec
vtr_schema | Create a star schema over linked vectra tables

## -- W --

warp | Resample or reproject a streamed raster onto a target grid
write_csv | Write query results or a data.frame to a CSV file
write_sqlite | Write query results or a data.frame to a SQLite table
write_tiff | Write query results to a GeoTIFF file
write_vtr | Write data to a .vtr file

## -- Z --

zonal | Summarise raster values within zones