FeatureCollection/reducing_feature_collection.ipynb

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        "<table class=\"ee-notebook-buttons\" align=\"left\">\n",
        "    <td><a target=\"_blank\"  href=\"https://github.com/giswqs/earthengine-py-notebooks/tree/master/FeatureCollection/reducing_feature_collection.ipynb\"><img width=32px src=\"https://www.tensorflow.org/images/GitHub-Mark-32px.png\" /> View source on GitHub</a></td>\n",
        "    <td><a target=\"_blank\"  href=\"https://nbviewer.jupyter.org/github/giswqs/earthengine-py-notebooks/blob/master/FeatureCollection/reducing_feature_collection.ipynb\"><img width=26px src=\"https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Jupyter_logo.svg/883px-Jupyter_logo.svg.png\" />Notebook Viewer</a></td>\n",
        "    <td><a target=\"_blank\"  href=\"https://colab.research.google.com/github/giswqs/earthengine-py-notebooks/blob/master/FeatureCollection/reducing_feature_collection.ipynb\"><img src=\"https://www.tensorflow.org/images/colab_logo_32px.png\" /> Run in Google Colab</a></td>\n",
        "</table>"
      ]
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    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Install Earth Engine API and geemap\n",
        "Install the [Earth Engine Python API](https://developers.google.com/earth-engine/python_install) and [geemap](https://geemap.org). The **geemap** Python package is built upon the [ipyleaflet](https://github.com/jupyter-widgets/ipyleaflet) and [folium](https://github.com/python-visualization/folium) packages and implements several methods for interacting with Earth Engine data layers, such as `Map.addLayer()`, `Map.setCenter()`, and `Map.centerObject()`.\n",
        "The following script checks if the geemap package has been installed. If not, it will install geemap, which automatically installs its [dependencies](https://github.com/giswqs/geemap#dependencies), including earthengine-api, folium, and ipyleaflet."
      ]
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "# Installs geemap package\n",
        "import subprocess\n",
        "\n",
        "try:\n",
        "    import geemap\n",
        "except ImportError:\n",
        "    print('Installing geemap ...')\n",
        "    subprocess.check_call([\"python\", '-m', 'pip', 'install', 'geemap'])"
      ],
      "outputs": [],
      "execution_count": null
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "import ee\n",
        "import geemap"
      ],
      "outputs": [],
      "execution_count": null
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Create an interactive map \n",
        "The default basemap is `Google Maps`. [Additional basemaps](https://github.com/giswqs/geemap/blob/master/geemap/basemaps.py) can be added using the `Map.add_basemap()` function. "
      ]
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "Map = geemap.Map(center=[40,-100], zoom=4)\n",
        "Map"
      ],
      "outputs": [],
      "execution_count": null
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Add Earth Engine Python script "
      ]
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "# Add Earth Engine dataset\n",
        "def areaDiff(feature):\n",
        "  area = feature.geometry().area().divide(1000 * 1000)\n",
        "  # Compute the differece between computed area and the area property.\n",
        "  diff = area.subtract(ee.Number.parse(feature.get('areasqkm')))\n",
        "  # Return the feature with the squared difference set to the 'diff' property.\n",
        "  return feature.set('diff', diff.pow(2))\n",
        "\n",
        "\n",
        "# Load watersheds from a data table and filter to the continental US.\n",
        "sheds = ee.FeatureCollection('USGS/WBD/2017/HUC06') \\\n",
        "  .filterBounds(ee.Geometry.Rectangle(-127.18, 19.39, -62.75, 51.29))\n",
        "\n",
        "# This function computes the squared difference between an area property\n",
        "# and area computed directly from the feature's geometry.\n",
        "# areaDiff = function(feature) {\n",
        "#   # Compute area in sq. km directly from the geometry.\n",
        "#   area = feature.geometry().area().divide(1000 * 1000)\n",
        "#   # Compute the differece between computed area and the area property.\n",
        "#   diff = area.subtract(ee.Number.parse(feature.get('areasqkm')))\n",
        "#   # Return the feature with the squared difference set to the 'diff' property.\n",
        "#   return feature.set('diff', diff.pow(2))\n",
        "# }\n",
        "\n",
        "# Calculate RMSE for population of difference pairs.\n",
        "rmse = ee.Number(\n",
        "  # Map the difference function over the collection.\n",
        "  sheds.map(areaDiff)\n",
        "  # Reduce to get the mean squared difference. \\\n",
        "  .reduceColumns(ee.Reducer.mean(), ['diff']) \\\n",
        "  .get('mean')\n",
        ") \\\n",
        ".sqrt()\n",
        "\n",
        "# Print the result.\n",
        "print('RMSE=', rmse.getInfo())\n",
        "\n"
      ],
      "outputs": [],
      "execution_count": null
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Display Earth Engine data layers "
      ]
    },
    {
      "cell_type": "code",
      "metadata": {},
      "source": [
        "Map.addLayerControl() # This line is not needed for ipyleaflet-based Map.\n",
        "Map"
      ],
      "outputs": [],
      "execution_count": null
    }
  ],
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