examples/example_healpy.ipynb

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 "cells": [
  {
   "cell_type": "markdown",
   "id": "0",
   "metadata": {},
   "source": [
    "# xdggs Healpix example"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "1",
   "metadata": {},
   "outputs": [],
   "source": [
    "import xarray as xr\n",
    "\n",
    "import xdggs"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2",
   "metadata": {},
   "source": [
    "Download the dataset here: https://zenodo.org/records/10075001"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3",
   "metadata": {},
   "outputs": [],
   "source": [
    "ds = xr.open_dataset(\"data/healpix_nolotation.nc\")\n",
    "\n",
    "ds = (\n",
    "    ds.load()\n",
    "    .drop_vars([\"latitude\", \"longitude\"])\n",
    "    .stack(cell=[\"x\", \"y\"], create_index=False)\n",
    ")\n",
    "\n",
    "ds.cell_ids.attrs = {\n",
    "    \"grid_name\": \"healpix\",\n",
    "    \"nside\": 4096,\n",
    "    \"nest\": True,\n",
    "}\n",
    "\n",
    "ds"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4",
   "metadata": {},
   "outputs": [],
   "source": [
    "ds_idx = ds.set_xindex(\"cell_ids\", xdggs.DGGSIndex)\n",
    "\n",
    "ds_idx"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5",
   "metadata": {},
   "source": [
    "## properties"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6",
   "metadata": {},
   "source": [
    "cell boundaries"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7",
   "metadata": {},
   "outputs": [],
   "source": [
    "cell_boundaries = ds_idx.dggs.cell_boundaries\n",
    "cell_boundaries"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "8",
   "metadata": {},
   "outputs": [],
   "source": [
    "df = (\n",
    "    cell_boundaries.to_dataset(name=\"geometry\")\n",
    "    .to_pandas()\n",
    "    .set_geometry(\"geometry\", crs=4326)\n",
    "    .set_index(\"cell_ids\")\n",
    ")\n",
    "df"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9",
   "metadata": {},
   "outputs": [],
   "source": [
    "df.explore(tiles=\"OpenStreetMap\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "10",
   "metadata": {},
   "source": [
    "## selection"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "11",
   "metadata": {},
   "source": [
    "by cell id"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "12",
   "metadata": {},
   "outputs": [],
   "source": [
    "ds_idx.sel(cell_ids=[11320973, 11320975])"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "13",
   "metadata": {},
   "source": [
    "by lat / lon coordinates"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "14",
   "metadata": {},
   "outputs": [],
   "source": [
    "ds_idx.dggs.sel_latlon([48.0, 48.1], -5.0)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "15",
   "metadata": {},
   "source": [
    "## assignment"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "16",
   "metadata": {},
   "outputs": [],
   "source": [
    "ds2 = ds_idx.dggs.assign_latlon_coords()\n",
    "ds2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "17",
   "metadata": {},
   "outputs": [],
   "source": [
    "result = ds_idx.dggs.sel_latlon(ds2.latitude, ds2.longitude)\n",
    "result"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "18",
   "metadata": {},
   "outputs": [],
   "source": [
    "xr.testing.assert_equal(result.drop_vars([\"latitude\", \"longitude\"]), ds)"
   ]
  }
 ],
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