google-maps-javascript-api-reference/CombineAndVisualizeMultipleData.html at master · ashwani-luhaniwal/google-maps-javascript-api-reference · GitHub

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<!--
    #########
    Combine and Visualize Multiple Data Sources
    #########
    This section shows you to display data from multiple sources on Google map. For example,
    the choropleth maps here uses two different sources to highlight various US states and
    display state-specific data.
    The map uses data from GeoJSON file to display polygons that define US state boundaries.
    It can also present data on the map corresponding to each state, which comes from a
    simulated query to the US Census API.
    Select a category of data from the control dropdown menu to update the polygons on the map.
    You can also hover over a state polygon to view state-specific information in a data
    box control on the map.
 -->

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Combine and Visualize Multiple Data Sources on Google Map</title>
        <meta name="viewport" content="initial-scale=1.0">
        <meta charset="UTF-8">
        <style type="text/css">
            html, body, #map {
                height: 100%;
                margin: 0;
                padding: 0;
                overflow: hidden;
            }
            .nicebox {
                position: absolute;
                text-align: center;
                font-family: 'Roboto', 'Arial', sans-serif;
                font-size: 13px;
                z-index: 5;
                box-shadow: 0 4px 6px -4px #333333;
                padding: 5px 10px;
                background: rgb(255, 255, 255);
                background: linear-gradient(to bottom, rgba(255, 255, 255, 1) 0%, rgba(245, 245, 245, 1) 100%);
                border: rgb(229, 229, 229) 1px solid;
            }
            #controls {
                top: 10px;
                left: 110px;
                width: 360px;
                height: 45px;
            }
            #data-box {
                top: 10px;
                left: 500px;
                height: 45px;
                line-height: 45px;
                display: none;
            }
            #census-variable {
                width: 360px;
                height: 20px;
            }
            #legend {
                display: flex;
                display: -webkit-box;
                padding-top: 7px;
            }
            .color-key {
                background: linear-gradient(to right,
                    hsl(5, 69%, 54%) 0%,
                    hsl(29, 71%, 51%) 17%,
                    hsl(54, 74%, 47%) 33%,
                    hsl(78, 76%, 44%) 50%,
                    hsl(102, 78%, 41%) 67%,
                    hsl(127, 81%, 37%) 83%,
                    hsl(151, 83%, 34%) 100%);
                flex: 1;
                -webkit-box-flex: 1;
                margin: 0 5px;
                text-align: left;
                font-size: 1.0em;
                line-height: 1.0em;
            }
            #data-value {
                font-size: 2.0em;
                font-weight: bold;
            }
            #data-label {
                font-size: 2.0em;
                font-weight: normal;
                padding-right: 10px;
            }
            #data-label:after {
                content: ':';
            }
            #data-caret {
                margin-left: -5px;
                display: none;
                font-size: 14px;
                width: 14px;
            }
        </style>
    </head>
    <body>
        <div id="controls" class="nicebox">
            <div>
                <!-- A control with a dropdown menu that has 5 different data options -->
                <select id="census-variable">
                    <option value="https://storage.googleapis.com/mapsdevsite/json/DP02_0066PE">Percent of population over 25 that completed high school</option>
                    <option value="https://storage.googleapis.com/mapsdevsite/json/DP05_0017E">Median Age</option>
                    <option value="https://storage.googleapis.com/mapsdevsite/json/DP05_0001E">Total Population</option>
                    <option value="https://storage.googleapis.com/mapsdevsite/json/DP02_0016E">Average Family Size</option>
                    <option value="https://storage.googleapis.com/mapsdevsite/json/DP03_0088E">Per-Capita Income</option>
                </select>
            </div>
            <!-- A map legend -->
            <div id="legend">
                <div id="census-min">min</div>
                <div class="color-key"><span id="data-caret">&#x25c6;</span></div>
                <div id="census-max">max</div>
            </div>
        </div>
        <!-- A data box displaying state-specific data which appears when you hover over a polygon -->
        <div id="data-box" class="nicebox">
            <label id="data-label" for="data-value"></label>
            <span id="data-value"></span>
        </div>

        <div id="map"></div>

        <script type="text/javascript">
            /*
                The stylers in the code below turn off the visibility of all "featureTypes" on the
                map like roads, points of interest, landscape, administrative areas, and all their
                "elementTypes".
            */
            var mapStyle = [{
                'featureType': 'all',
                'elementType': 'all',
                'stylers': [{'visibility': 'off'}]
            }, {
                'featureType': 'landscape',
                'elementType': 'geometry',
                'stylers': [{'visibility': 'on'}, {'color': '#fcfcfc'}]
            }, {
                'featureType': 'water',
                'elementType': 'labels',
                'stylers': [{'visibility': 'off'}]
            }, {
                'featureType': 'water',
                'elementType': 'geometry',
                'stylers': [{'visibility': 'on'}, {'hue': '#5f94ff'}, {'lightness': 60}]
            }];
            var map;
            var censusMin = Number.MAX_VALUE, censusMax = -Number.MAX_VALUE;

            // initMap function initializes the map object and adds map when the web page loads.
            function initMap() {

                // load the map
                map = new google.maps.Map(document.getElementById('map'), {
                    center: {lat: 40, lng: -100},
                    zoom: 4,
                    styles: mapStyle
                });

                // set up the style rules and events for google.maps.Data
                map.data.setStyle(styleFeature);
                map.data.addListener('mouseover', mouseInToRegion);
                map.data.addListener('mouseout', mouseOutOfRegion);

                // wire up the button
                var selectBox = document.getElementById('census-variable');
                google.maps.event.addDomListener(selectBox, 'change', function() {
                    clearCensusData();
                    loadCensusData(selectBox.options[selectBox.selectedIndex].value);
                });

                // state polygons only need to be loaded once, do them now
                loadMapShapes();
            }

            /*
                On selecting a data source option from the map control dropdown menu, the map queries
                the US Census Data API for the specified variable. To connect the census data with
                the shape data, the code sets the "idPropertyName" to 'STATE', which is a common
                key in both the Census data and in the GeoJson properties.
            */
            // Loads the state boundary polygons from a GeoJSON source
            function loadMapShapes() {
                // load US state outline polygons from a GeoJSON file
                map.data.loadGeoJson('https://storage.googleapis.com/mapsdevsite/json/states.js', { idPropertyName: 'STATE' });

                // wait for the request to complete by listening for the first feature to be added
                google.maps.event.addListenerOnce(map.data, 'addfeature', function() {
                    google.maps.event.trigger(document.getElementById('census-variable'), 'change');
                });
            }

            // Loads the census data from a simulated API call to the US Census API.
            // @param {string} variable
            function loadCensusData(variable) {
                // load the requested variable from the census API (using local copies)
                var xhr = new XMLHttpRequest();
                xhr.open('GET', variable + '.json');
                xhr.onload = function() {
                    var censusData = JSON.parse(xhr.responseText);
                    censusData.shift(); // the first row contains column names
                    censusData.forEach(function(row) {
                        var censusVariable = parseFloat(row[0]);
                        var stateId = row[1];

                        // keep track of min and max values
                        if (censusVariable < censusMin) {
                            censusMin = censusVariable;
                        }
                        if (censusVariable > censusMax) {
                            censusMax = censusVariable;
                        }

                        // update the existing row with the new data
                        map.data.getFeatureById(stateId).setProperty('census_variable', censusVariable);
                    });

                    // update and display the legend
                    document.getElementById('census-min').textContent = censusMin.toLocaleString();
                    document.getElementById('census-max').textContent = censusMax.toLocaleString();
                };

                xhr.send();
            }

            // Removes census data from each shape on the map and resets the UI
            function clearCensusData() {
                censusMin = Number.MAX_VALUE;
                censusMax = -Number.MAX_VALUE;
                map.data.forEach(function(row) {
                    row.setProperty('census_variable', undefined);
                });
                document.getElementById('data-box').style.display = 'none';
                document.getElementById('data-caret').style.display = 'none';
            }

            // Applies a gradient style based on 'census_variable' column.
            // This the callback passed to data.setStyle() and is called for each row in
            // the data set. Check out the docs for Data.StylingFunction.
            // @param {google.maps.Data.Feature} feature
            function styleFeature(feature) {
                var low = [5, 69, 54];  // color of smallest datum
                var high = [151, 83, 34];   // color of largest datum

                // delta represents where the value sits between the min and max
                var delta = (feature.getProperty('census_variable') - censusMin) / (censusMax - censusMin);

                var color = [];
                for (var i = 0; i < 3; i++) {
                    // calculate an integer color based on the delta
                    color[i] = (high[i] - low[i]) * delta + low[i];
                }

                // determine whether to show this shape or not
                var showRow = true;
                if (feature.getProperty('census_variable') == null || isNaN(feature.getProperty('census_variable'))) {
                    showRow = false;
                }

                var outlineWeight = 0.5, zIndex = 1;
                if (feature.getProperty('state') === 'hover') {
                    outlineWeight = zIndex = 2;
                }

                return {
                    strokeWeight: outlineWeight,
                    strokeColor: '#fff',
                    zIndex: zIndex,
                    fillColor: 'hsl(' + color[0] + ', ' + color[1] + '%, ' + color[2] + '%)',
                    fillOpacity: 0.75,
                    visible: showRow
                };
            }

            // Responds to the mouse-in event on a map shape (state)
            // @param {?google.maps.MouseEvent} e
            function mouseInToRegion(e) {
                // set the hover state so the setStyle function can change the border
                e.feature.setProperty('state', 'hover');

                var percent = (e.feature.getProperty('census_variable') - censusMin) / (censusMax - censusMin) * 100;

                // update the label
                document.getElementById('data-label').textContent = e.feature.getProperty('NAME');
                document.getElementById('data-value').textContent = e.feature.getProperty('census_variable').toLocaleString();
                document.getElementById('data-box').style.display = 'block';
                document.getElementById('data-caret').style.display = 'block';
                document.getElementById('data-caret').style.paddingLeft = percent + '%';
            }

            // Respond to mouse-out event on a map shape (state)
            // @param (?google.maps.MouseEvent) e
            function mouseOutOfRegion(e) {
                // reset the hover state, returning the border to normal
                e.feature.setProperty('state', 'normal');
            }
        </script>
        <script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCgncHE9VhehCiKENUJB0y19GURax6WXqk&callback=initMap" async defer></script>
    </body>
</html>