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I am new to using Mosaic on Databricks. The task is to create a Heatmap with the counts within Hexagons of H3 resolution. Since the dataset is quite large I am opting for Mosaic. As the first step I am trying to create the hexagons covering the given area but the following code does not generate hexagons covering the full square as illustrated below:

from pyspark.sql.functions import *
from mosaic import enable_mosaic
enable_mosaic(spark, dbutils)

from pyspark import SparkContext
from pyspark.sql import functions as F
import mosaic as mos


from mosaic import st_point

lons = [-80., -80., -70., -70., -80.]
lats = [ 35.,  45.,  45.,  35.,  35.]

bounds_df = (
  spark
  .createDataFrame({"lon": lon, "lat": lat} for lon, lat in zip(lons, lats))
  .coalesce(1)
  .withColumn("point_geom", st_point("lon", "lat"))
)
bounds_df.show()

from mosaic import st_makeline

bounds_df = (
  bounds_df
  .groupBy()
  .agg(F.collect_list("point_geom").alias("bounding_coords"))
  .select(st_makeline("bounding_coords").alias("bounding_ring"))
)
bounds_df.show()

from mosaic import st_makepolygon

bounds_df = bounds_df.select(st_makepolygon("bounding_ring").alias("bounds"))
bounds_df.show()


hexs = (bounds_df
       .select(mos.mosaic_explode("bounds", lit(5)))
       .select("index.*")
    )

hexs.show()

%%mosaic_kepler
hexs "index_id" "h3"

enter image description here

Do you know why there are gaps in between the hexagons?

1 Answer 1

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This function only displays a sample of the dataset hence you see the gaps between the hexagons.

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