sparklyr.sedona is now accessible
because the sparklyr-based R interface for Apache Sedona.
To put in sparklyr.sedona from GitHub utilizing
the remotes package deal
, run
remotes::install_github(repo = "apache/incubator-sedona", subdir = "R/sparklyr.sedona")On this weblog publish, we’ll present a fast introduction to sparklyr.sedona, outlining the motivation behind
this sparklyr extension, and presenting some instance sparklyr.sedona use circumstances involving Spark spatial RDDs,
Spark dataframes, and visualizations.
Motivation for sparklyr.sedona
A suggestion from the
mlverse survey results earlier
this 12 months talked about the necessity for up-to-date R interfaces for Spark-based GIS frameworks.
Whereas trying into this suggestion, we discovered about
Apache Sedona, a geospatial knowledge system powered by Spark
that’s fashionable, environment friendly, and straightforward to make use of. We additionally realized that whereas our pals from the
Spark open-source neighborhood had developed a
sparklyr extension for GeoSpark, the
predecessor of Apache Sedona, there was no related extension making more moderen Sedona
functionalities simply accessible from R but.
We subsequently determined to work on sparklyr.sedona, which goals to bridge the hole between
Sedona and R.
The lay of the land
We hope you might be prepared for a fast tour via a few of the RDD-based and
Spark-dataframe-based functionalities in sparklyr.sedona, and in addition, some bedazzling
visualizations derived from geospatial knowledge in Spark.
In Apache Sedona,
Spatial Resilient Distributed Datasets(SRDDs)
are fundamental constructing blocks of distributed spatial knowledge encapsulating
“vanilla” RDDs of
geometrical objects and indexes. SRDDs assist low-level operations comparable to Coordinate Reference System (CRS)
transformations, spatial partitioning, and spatial indexing. For instance, with sparklyr.sedona, SRDD-based operations we will carry out embody the next:
- Importing some exterior knowledge supply right into a SRDD:
library(sparklyr)
library(sparklyr.sedona)
sedona_git_repo <- normalizePath("~/incubator-sedona")
data_dir <- file.path(sedona_git_repo, "core", "src", "check", "sources")
sc <- spark_connect(grasp = "native")
pt_rdd <- sedona_read_dsv_to_typed_rdd(
sc,
location = file.path(data_dir, "arealm.csv"),
sort = "level"
)- Making use of spatial partitioning to all knowledge factors:
sedona_apply_spatial_partitioner(pt_rdd, partitioner = "kdbtree")- Constructing spatial index on every partition:
sedona_build_index(pt_rdd, sort = "quadtree")- Becoming a member of one spatial knowledge set with one other utilizing “include” or “overlap” because the be a part of predicate:
polygon_rdd <- sedona_read_dsv_to_typed_rdd(
sc,
location = file.path(data_dir, "primaryroads-polygon.csv"),
sort = "polygon"
)
pts_per_region_rdd <- sedona_spatial_join_count_by_key(
pt_rdd,
polygon_rdd,
join_type = "include",
partitioner = "kdbtree"
)It’s value mentioning that sedona_spatial_join() will carry out spatial partitioning
and indexing on the inputs utilizing the partitioner and index_type provided that the inputs
are usually not partitioned or listed as specified already.
From the examples above, one can see that SRDDs are nice for spatial operations requiring
fine-grained management, e.g., for guaranteeing a spatial be a part of question is executed as effectively
as potential with the precise forms of spatial partitioning and indexing.
Lastly, we will strive visualizing the be a part of outcome above, utilizing a choropleth map:
which provides us the next:
Wait, however one thing appears amiss. To make the visualization above look nicer, we will
overlay it with the contour of every polygonal area:
contours <- sedona_render_scatter_plot(
polygon_rdd,
resolution_x = 1000,
resolution_y = 600,
output_location = tempfile("scatter-plot-"),
boundary = c(-126.790180, -64.630926, 24.863836, 50.000),
base_color = c(255, 0, 0),
browse = FALSE
)
sedona_render_choropleth_map(
pts_per_region_rdd,
resolution_x = 1000,
resolution_y = 600,
output_location = tempfile("choropleth-map-"),
boundary = c(-126.790180, -64.630926, 24.863836, 50.000),
base_color = c(63, 127, 255),
overlay = contours
)which provides us the next:
With some low-level spatial operations taken care of utilizing the SRDD API and
the precise spatial partitioning and indexing knowledge buildings, we will then
import the outcomes from SRDDs to Spark dataframes. When working with spatial
objects inside Spark dataframes, we will write high-level, declarative queries
on these objects utilizing dplyr verbs along with Sedona
spatial UDFs, e.g.
, the
following question tells us whether or not every of the 8 nearest polygons to the
question level comprises that time, and in addition, the convex hull of every polygon.
tbl <- DBI::dbGetQuery(
sc, "SELECT ST_GeomFromText("POINT(-66.3 18)") AS `pt`"
)
pt <- tbl$pt[[1]]
knn_rdd <- sedona_knn_query(
polygon_rdd, x = pt, ok = 8, index_type = "rtree"
)
knn_sdf <- knn_rdd %>%
sdf_register() %>%
dplyr::mutate(
contains_pt = ST_contains(geometry, ST_Point(-66.3, 18)),
convex_hull = ST_ConvexHull(geometry)
)
knn_sdf %>% print()# Supply: spark<?> [?? x 3]
geometry contains_pt convex_hull
<checklist> <lgl> <checklist>
1 <POLYGON ((-66.335674 17.986328… TRUE <POLYGON ((-66.335674 17.986328,…
2 <POLYGON ((-66.335432 17.986626… TRUE <POLYGON ((-66.335432 17.986626,…
3 <POLYGON ((-66.335432 17.986626… TRUE <POLYGON ((-66.335432 17.986626,…
4 <POLYGON ((-66.335674 17.986328… TRUE <POLYGON ((-66.335674 17.986328,…
5 <POLYGON ((-66.242489 17.988637… FALSE <POLYGON ((-66.242489 17.988637,…
6 <POLYGON ((-66.242489 17.988637… FALSE <POLYGON ((-66.242489 17.988637,…
7 <POLYGON ((-66.24221 17.988799,… FALSE <POLYGON ((-66.24221 17.988799, …
8 <POLYGON ((-66.24221 17.988799,… FALSE <POLYGON ((-66.24221 17.988799, …Acknowledgements
The writer of this weblog publish wish to thank Jia Yu,
the creator of Apache Sedona, and Lorenz Walthert for
their suggestion to contribute sparklyr.sedona to the upstream
incubator-sedona repository. Jia has supplied
intensive code-review suggestions to make sure sparklyr.sedona complies with coding requirements
and greatest practices of the Apache Sedona undertaking, and has additionally been very useful within the
instrumentation of CI workflows verifying sparklyr.sedona works as anticipated with snapshot
variations of Sedona libraries from improvement branches.
The writer can be grateful for his colleague Sigrid Keydana
for priceless editorial options on this weblog publish.
That’s all. Thanks for studying!
Photograph by NASA on Unsplash
