adds custom datasource for torque

lib/torque/renderer/datasource.js

@@ -0,0 +1,52 @@
+var d3 = require('d3');
+var jenks = require('turf-jenks');
+
+function TorqueDataSource (tiles) {
+  this.tiles = tiles
+}
+
+module.exports = TorqueDataSource
+
+TorqueDataSource.prototype.getName = function () {
+  return 'TorqueDataSource'
+}
+
+TorqueDataSource.prototype.getRamp = function (column, bins, method, callback) {
+  var ramp = []
+  var error = null
+  var values = Object.keys(this.tiles).map(function (t) {
+    return this.tiles[t].renderData;
+  }.bind(this)).reduce(function (p,c,i) {
+    for(var i = 0; i<c.length; i++) {
+      p.push(c[i]);
+    }
+    return p;
+  },[]);
+  var extent = d3.extent(values);
+  if (!method || method === 'equal' || method === 'jenks') {
+    var scale = d3.scale.linear().domain([0, bins]).range(extent)
+    ramp = d3.range(bins).map(scale)
+  } else if (method === 'quantiles') {
+    ramp = d3.scale.quantile().range(d3.range(bins)).domain(values).quantiles()
+  } else if (method === 'headstails') {
+    var sortedValues = values.sort(function(a, b) {
+      return a - b;
+    });
+    if (sortedValues.length < bins) {
+      error = 'Number of bins should be lower than total number of rows'
+    } else if (sortedValues.length === bins) {
+      ramp = sortedValues;
+    } else {
+      var mean = d3.mean(sortedValues);
+      ramp.push(mean);
+      for (var i = 1; i < bins; i++) {
+        ramp.push(d3.mean(sortedValues.filter(function (v) {
+          return v > ramp[length - 1];
+        })));
+      }
+    }
+  } else {
+    error = new Error('Quantification method ' + method + ' is not supported')
+  }
+  callback(error, ramp)
+}