比较D3.js中的两个时间对象

Question

In D3.js i am currently trying to populate an empty array (array contains only time stamp after every 5 minutes) based on data array contains that time or not . If data array contains the time, it should copy the value otherwise null. But when i am trying to compare the two time objects its not working correctly.

Following is the code (the current code is not copying values but printing to make debugging easier):

var data = [{"mytime": "2015-12-01T23:10:00.000Z", "value": 64},
{"mytime": "2015-12-01T23:15:00.000Z", "value": 67},
{"mytime": "2015-12-01T23:20:00.000Z", "value": 70},
{"mytime": "2015-12-01T23:25:00.000Z", "value": 64},
{"mytime": "2015-12-01T23:30:00.000Z", "value": 72},
{"mytime": "2015-12-01T23:35:00.000Z", "value": 75},
{"mytime": "2015-12-01T23:40:00.000Z", "value": 71},
{"mytime": "2015-12-01T23:45:00.000Z", "value": 80},
{"mytime": "2015-12-02T00:00:00.000Z", "value": 80},
{"mytime": "2015-12-02T00:05:00.000Z", "value": 85}
];

var parseDate = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ").parse;

data.forEach(function(d) {
          d.mytime = parseDate(d.mytime);
 });

var act_data = [];

  var x_extent = d3.extent(data, function(d){
      return d['mytime']});

  time_arr = d3.time.minute.range(x_extent[0],x_extent[1],5);
  for(var key in time_arr){
  var temp;
  temp = contains(data,time_arr[key],'mytime');
}


function contains(data,value,variable)
{
  var i =data.length;
  while(i--){

   if (data[i][variable] === value)
   {
    console.log('found');
    return i;
   } 
  }
  return false;
}

Output should be this:

data = [{"mytime": "2015-12-01T23:10:00.000Z", "value": 64},
{"mytime": "2015-12-01T23:15:00.000Z", "value": 67},
{"mytime": "2015-12-01T23:20:00.000Z", "value": 70},
{"mytime": "2015-12-01T23:25:00.000Z", "value": 64},
{"mytime": "2015-12-01T23:30:00.000Z", "value": 72},
{"mytime": "2015-12-01T23:35:00.000Z", "value": 75},
{"mytime": "2015-12-01T23:40:00.000Z", "value": 71},
{"mytime": "2015-12-01T23:45:00.000Z", "value": 80},
{"mytime": "2015-12-01T23:50:00.000Z", "value": null},
{"mytime": "2015-12-01T23:55:00.000Z", "value": null},
{"mytime": "2015-12-02T00:00:00.000Z", "value": 80},
{"mytime": "2015-12-02T00:05:00.000Z", "value": 85}
];

Answer 1

You can use

• d3.time.format to parse and format your dates
• d3.extent to determine the boundaries of your timestamps
• d3.time.scale to generate the ticks you want to output
• and d3.map to hash your input and determine if a value exists

This gives us

var data = [...];

// for parsing and formatting
var timeformat = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ");

// range to operate on
var extent = d3.extent(data, function(d){ 
    return timeformat.parse(d.mytime); 
});

// scale representing the time stamps
var scale = d3.time.scale()
    .domain(extent) // the boundaries
    .ticks(d3.time.minute, 5); // 5 minutes intervals

// easier to determine if a value exists
var hashed = d3.map(data, function(d) { return d.mytime; });

// or if your version < 3.5
/*
var hashed = d3.map();
data.forEach(function(d) { 
    hashed.set(d.mytime, d);
});
*/


// transforms the scale into the desired output
var res = scale.map(function(t) {
    var ft = timeformat(t);
    return {
        mytime: ft,
        value: (hashed.has(ft)) ? hashed.get(ft).value : null
    };
});

And a demo http://jsfiddle.net/nikoshr/qxcLry8z/

 var data = [ {"mytime": "2015-12-01T23:10:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:15:00.000Z", "value": 67}, {"mytime": "2015-12-01T23:20:00.000Z", "value": 70}, {"mytime": "2015-12-01T23:25:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:30:00.000Z", "value": 72}, {"mytime": "2015-12-01T23:35:00.000Z", "value": 75}, {"mytime": "2015-12-01T23:40:00.000Z", "value": 71}, {"mytime": "2015-12-01T23:45:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:00:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:05:00.000Z", "value": 85} ]; var timeformat = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ"); var extent = d3.extent(data, function(d){ return timeformat.parse(d.mytime); }); var scale = d3.time.scale() .domain(extent) .ticks(d3.time.minute, 5); var hashed = d3.map(); data.forEach(function(d) { hashed.set(d.mytime, d); }); var res = scale.map(function(t) { var ft = timeformat(t); return { mytime: ft, value: (hashed.has(ft)) ? hashed.get(ft).value : null }; }); var $table = $('<table></table>'); res.forEach(function(d) { $table.append('<tr><td>'+d.mytime+'</td><td>'+d.value+'</td></tr>') }); $('body').append($table); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script> 

Answer 2

You can do it like this:

var extent = d3.extent(data, function(d){ return d.mydate});//get the max min limit
var data1 = []; make an empty array
for (var i =0; i < data.length -1; i++){
    var diff = data[i + 1].mytime.getTime() - data[i].mytime.getTime();
    if (diff <= 300000){ //less than equal to 5 minutes
        data1.push(data[i])
    } else { //greater than 5 minutes
      var t1 = new Date(data[i].mytime.getTime() + 300000)
        var t2 = new Date(data[i +1].mytime.getTime() - 300000)
        data1.push({"mytime": t1, "value": null})
        data1.push({"mytime": t2, "value": null})
    }
}
data1.push(data[data.length -1]); //take the last value as it was not processed
data = data1

working code here

Answer 3

With the advent of ES6 there are more options available to tackle the task. Depending on the browser versions one needs to support, the following code might be a viable approach. I have successfully tested this on Chrome 49 and FF 45.

The solution adds a custom generator function to the data array that will return a Generator object which conforms to the new iteration protocols . This will iterate over the data array and fill in any gaps it detects along the way with objects having their value property set to null .

The snippet further makes use of the spread operator to create a new array and fill it by implicitly invoking the iterator.

data[Symbol.iterator] = function*() {
  var i = 0,
      t = this[0],
      nextStep;
  while (i < this.length) {
    nextStep = t.mytime.getTime() + FIVE_MINUTES_IN_MS;
    yield t = nextStep < this[i].mytime.getTime()
      ? {"mytime": new Date(nextStep), "value": null}
      : this[i++];
  }
};


// use the spread operator to create a new array which will implicitly call
// the iterator
data = [...data];

Have a look at the following snippet for a demo working in Chrome 49 and FF 45:

 "use strict"; /////////////////////////////////////////////////////////////////////////// // Setup /////////////////////////////////////////////////////////////////////////// const FIVE_MINUTES_IN_MS = 5 * 60 * 1000; var data = [ {"mytime": "2015-12-01T23:10:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:15:00.000Z", "value": 67}, {"mytime": "2015-12-01T23:20:00.000Z", "value": 70}, {"mytime": "2015-12-01T23:25:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:30:00.000Z", "value": 72}, {"mytime": "2015-12-01T23:35:00.000Z", "value": 75}, {"mytime": "2015-12-01T23:40:00.000Z", "value": 71}, {"mytime": "2015-12-01T23:45:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:00:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:05:00.000Z", "value": 85} ]; var parse = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ").parse; data.forEach(function(d) { d.mytime = parse(d.mytime); }); /////////////////////////////////////////////////////////////////////////// // Implement iterator to fill in gaps in data array /////////////////////////////////////////////////////////////////////////// data[Symbol.iterator] = function*() { var i = 0, t = this[0], nextStep; while (i < this.length) { nextStep = t.mytime.getTime() + FIVE_MINUTES_IN_MS; yield t = nextStep < this[i].mytime.getTime() ? {"mytime": new Date(nextStep), "value": null} : this[i++]; } }; // use the spread operator to create a new array which will implicitly call the iterator data = [...data]; /////////////////////////////////////////////////////////////////////////// // Just output below. /////////////////////////////////////////////////////////////////////////// //console.dir(data); d3.select("body").append("div") .style({ "font-family": "monospace", "white-space": "pre" }) .text(JSON.stringify(data, null, 2)); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script> 

---

Alternatively, you may provide an explicit implementation of the iterator protocol. This is a little more verbose to write but does not change the overall concept:

data[Symbol.iterator] = function() {
  var self = this;
  return {
    i: 0,
    t: self[0],
    next() {
      if (this.i < self.length) {
        var nextStep = this.t.mytime.getTime() + FIVE_MINUTES_IN_MS;
        this.t = nextStep < self[this.i].mytime.getTime()
          ? { "mytime": new Date(nextStep), "value": null }
          : self[this.i++];
        return {
          value: this.t,
          done:  false
        }
      } else {
        return {
          done: true
        }
      } 
    }
  }
};

The following snippet demonstrates this:

 "use strict"; /////////////////////////////////////////////////////////////////////////// // Setup /////////////////////////////////////////////////////////////////////////// const FIVE_MINUTES_IN_MS = 5 * 60 * 1000; var data = [ {"mytime": "2015-12-01T23:10:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:15:00.000Z", "value": 67}, {"mytime": "2015-12-01T23:20:00.000Z", "value": 70}, {"mytime": "2015-12-01T23:25:00.000Z", "value": 64}, {"mytime": "2015-12-01T23:30:00.000Z", "value": 72}, {"mytime": "2015-12-01T23:35:00.000Z", "value": 75}, {"mytime": "2015-12-01T23:40:00.000Z", "value": 71}, {"mytime": "2015-12-01T23:45:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:00:00.000Z", "value": 80}, {"mytime": "2015-12-02T00:05:00.000Z", "value": 85} ]; var parse = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ").parse; data.forEach(function(d) { d.mytime = parse(d.mytime); }); /////////////////////////////////////////////////////////////////////////// // Implement iterator to fill in gaps in data array /////////////////////////////////////////////////////////////////////////// data[Symbol.iterator] = function() { var self = this; return { i: 0, t: self[0], next() { if (this.i < self.length) { var nextStep = this.t.mytime.getTime() + FIVE_MINUTES_IN_MS; this.t = nextStep < self[this.i].mytime.getTime() ? { "mytime": new Date(nextStep), "value": null } : self[this.i++]; return { value: this.t, done: false } } else { return { done: true } } } } }; // use the spread operator to create a new array which will implicitly call the iterator data = [...data]; /////////////////////////////////////////////////////////////////////////// // Just output below. /////////////////////////////////////////////////////////////////////////// //console.dir(data); d3.select("body").append("div") .style({ "font-family": "monospace", "white-space": "pre" }) .text(JSON.stringify(data, null, 2)); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>