按距离查询客户端统计数据

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view.on("drag", function(event) {
  // query the layer view for each pointer drag event
  // then display the results in the charts
  queryStatsOnDrag(layerView, event).then(updateCharts);
});

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const query = layerView.layer.createQuery();
// converts the screen point to a map point
// the event object is returned from the drag event
query.geometry = view.toMap(event);
// queries all features within 1 mile of the point
query.distance = 1;
query.units = "miles";

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// clone the query object from the previous snippet
const statsQuery = query.clone();

// date used to calculate the average time a case has been opened
const dataDownloadDate = Date.UTC(2018, 6, 5);

// Create the statistic definitions for querying stats from the layer view
// the `onStatisticField` property can reference a field name or a SQL expression
// `outStatisticFieldName` is the name of the statistic you will reference in the result
// `statisticType` can be sum, avg, min, max, count, stddev
const statDefinitions = [
  // Age of crime since it was reported in years

  {
    onStatisticField: "(" + dataDownloadDate + " - milliseconds) / (1000 * 60 * 60 * 24 * 365.25)",
    outStatisticFieldName: "avg_open_time_years",
    statisticType: "avg"
  },

  // total homicides

  {
    onStatisticField: "1",
    outStatisticFieldName: "total",
    statisticType: "count"
  },

  // crime disposition (aka crime status)
  //
  // Since this is a string field, we can use a similar technique to sum
  // the total of each status of the crime

  {
    onStatisticField: "CASE WHEN disposition = 'Closed by arrest' THEN 1 ELSE 0 END",
    outStatisticFieldName: "num_closed_arrest",
    statisticType: "sum"
  },
  {
    onStatisticField: "CASE WHEN disposition = 'Open/No arrest' THEN 1 ELSE 0 END",
    outStatisticFieldName: "num_open",
    statisticType: "sum"
  },
  {
    onStatisticField: "CASE WHEN disposition = 'Closed without arrest' THEN 1 ELSE 0 END",
    outStatisticFieldName: "num_closed_no_arrest",
    statisticType: "sum"
  },

  // average victim age
  //
  // Some victim ages are unknown and indicated with a -99. We'll
  // use an expression to treat those unknown ages as 0. This will
  // skew the average age slightly downward since we can't exclude those
  // values without a where clause. Do use a where clause, we could execute
  // a separate query

  {
    onStatisticField: "CASE WHEN victim_age_years = -99 THEN 0 ELSE victim_age_years END",
    outStatisticFieldName: "avg_age",
    statisticType: "avg"
  }
];

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// add the stat definitions to the the statistics query object cloned earlier
statsQuery.outStatistics = statDefinitions;

// execute the query for all features in the layer view
return layerView.queryFeatures(statsQuery).then(
  function(response) {
    const stats = response.features[0].attributes;
    return stats;
  },
  function(e) {
    console.error(e);
  }
);

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// clone the query object from the previous steps
const openStatsQuery = statsQuery.clone();
// limit the results to only the crimes that did not result in an arrest
openStatsQuery.where = "disposition = 'Open/No arrest'";

// execute the query for only unsolved homicides in the layer view
return layerView.queryFeatures(openStatsQuery).then(
  function(response) {
    const stats = response.features[0].attributes;
    return stats;
  },
  function(e) {
    console.error(e);
  }
);