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D3 Real Time Chart with Multiple Data Streams

D3 Based Real Time Chart with Multiple Streams

The real time chart is a resuable Javascript component that accepts real time data. The purpose is to show the arrival time of real time events (or lack thereof), piped to the browser (for example via Websockets). Various attributes of each event can be articulated using size, color and opacity of the object generated for the event.

The component allows multiple asynchronous data streams to be viewed, each in a horizontal band across the SVG. New data streams can be added dynamically (as they are discovered by the caller over time), simply by calling the yDomain method with the new array of data series names. The chart will automatically fit the new data series into the available space in the SVG.

The chart's time domain is moving with the passage of time. That means that any data placed in the chart eventually will age out and leave the chart. Currently, the chart history is capped at five minutes (but can be changed by modifying the component).

In addition to the main chart, the component also manages a navigation window with a viewport (using d3.brush) that can moved and sized to view an arbitrary portion of the time series data.

A nice future capability is to allow the caller to dynamically specify the type of object to be created for each data item. The infrastructure is in place to dynamically create different svg objects on the fly (using the document.createElementNS() function). However, given the current data binding mechanism (lacking a "key function"), the data is just "passing through" already created elements (not necessarily of the same type as what the is specified by the data).

Another nice capability would be to use d3 transitions to create smooth horizontal scrolling, as opposed to the current 200ms leftward jump. Any idea how to implement this is appreciated.

View the component in action at bl.ocks.org here, Repos: GitHub Gist here, GitHub here

The component is a derivative of D3 Based Real Time Chart.

The component adheres to the pattern described in Towards Reusable Chart.

Use the component like so:

// create the real time chart
var chart = realTimeChartMulti()
    .width(900)               // width in pixels of chart; mandatory
    .height(350)              // height in pixels of chart; mandatory
    .yDomain(["Category1"])   // initial categories/data streams (note array),  mandatory
    .title("Chart Title")     // optional
    .yTitle("Categories")     // optional
    .xTitle("Time")           // optional
    .border(true);            // optional

// invoke the chart
var chartDiv = d3.select("#viewDiv").append("div")
    .attr("id", "chartDiv")
    .call(chart);

// create data item
var obj = {
  time: new Date().getTime(), // mandatory
  category: "Category1",      // mandatory
  type: "rect",               // optional (defaults to circle)
  color: "red",               // optional (defaults to black)
  opacity: 0.8,               // optional (defaults to 1)
  size: 5,                    // optional (defaults to 6)
};

// send the data item to the chart
chart.datum(obj);  

// to dynamically add a data series, just call yDomain with a new array of data series names
// (of course, all data passed to the chart will need to reference one of these categories)
// the data series can dynamically be (re-)sorted in arbitrary order; the chart will update accordingly
chart.yDomain(["Category1", "Category2"]);  

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<!-- Author: Bo Ericsson -->
<title>Real Time Chart Multi</title>
<link rel=stylesheet type=text/css href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/2.3.2/css/bootstrap.min.css" media="all">
<!--<link rel=stylesheet type=text/css href="../_lib/bootstrap.min.css" media="all">-->
<style>
.axis text {
font: 10px sans-serif;
}
.chartTitle {
font-size: 12px;
font-weight: bold;
text-anchor: middle;
}
.axis .title {
font-weight: bold;
text-anchor: middle;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.x.axis path {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.nav .area {
fill: lightgrey;
stroke-width: 0px;
}
.nav .line {
fill: none;
stroke: darkgrey;
stroke-width: 1px;
}
.viewport {
stroke: grey;
fill: black;
fill-opacity: 0.3;
}
.viewport .extent {
fill: green;
}
.well {
padding-top: 0px;
padding-bottom: 0px;
}
</style>
<body>
<div style="max-width: 900px; max-height: 400px; padding: 10px">
<div class="well">
<h4>D3 Based Real Time Chart with Multiple Data Streams
</div>
<input id="debug" type="checkbox" name="debug" value="debug" style="margin-bottom: 10px" /> Debug
<input id="halt" type="checkbox" name="halt" value="halt" style="margin-bottom: 10px" /> Halt
<div id="viewDiv"></div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js"></script>
<!--<script src="../_lib/d3.min.js"></script>-->
<script src="realTimeChartMulti.js"></script>
<script>
'use strict';
// create the real time chart
var chart = realTimeChartMulti()
.title("Chart Title")
.yTitle("Categories")
.xTitle("Time")
.yDomain(["Category1"]) // initial y domain (note array)
.border(true)
.width(900)
.height(350);
// invoke the chart
var chartDiv = d3.select("#viewDiv").append("div")
.attr("id", "chartDiv")
.call(chart);
// alternative and equivalent invocation
//chart(chartDiv);
// event handler for debug checkbox
d3.select("#debug").on("change", function() {
var state = d3.select(this).property("checked")
chart.debug(state);
})
// event handler for halt checkbox
d3.select("#halt").on("change", function() {
var state = d3.select(this).property("checked")
chart.halt(state);
})
// configure the data generator
// mean and deviation for generation of time intervals
var tX = 5; // time constant, multiple of one second
var meanMs = 1000 * tX, // milliseconds
dev = 200 * tX; // std dev
// define time scale
var timeScale = d3.scale.linear()
.domain([300 * tX, 1700 * tX])
.range([300 * tX, 1700 * tX])
.clamp(true);
// define function that returns normally distributed random numbers
var normal = d3.random.normal(meanMs, dev);
// define color scale
var color = d3.scale.category10();
// in a normal use case, real time data would arrive through the network or some other mechanism
var d = -1;
var shapes = ["rect", "circle"];
var timeout = 0;
// define data generator
function dataGenerator() {
setTimeout(function() {
// add categories dynamically
d++;
switch (d) {
case 5:
chart.yDomain(["Category1", "Category2"]);
break;
case 10:
chart.yDomain(["Category1", "Category2", "Category3"]);
break;
default:
}
// output a sample for each category, each interval (five seconds)
chart.yDomain().forEach(function(cat, i) {
// create randomized timestamp for this category data item
var now = new Date(new Date().getTime() + i * (Math.random() - 0.5) * 1000);
// create new data item
var obj;
var doSimple = false;
if (doSimple) {
obj = {
// simple data item (simple black circle of constant size)
time: now,
color: "black",
opacity: 1,
category: "Category" + (i + 1),
type: "circle",
size: 5,
};
} else {
obj = {
// complex data item; four attributes (type, color, opacity and size) are changing dynamically with each iteration (as an example)
time: now,
color: color(d % 10),
opacity: Math.max(Math.random(), 0.3),
category: "Category" + (i + 1),
//type: shapes[Math.round(Math.random() * (shapes.length - 1))], // the module currently doesn't support dynamically changed svg types (need to add key function to data, or method to dynamically replace svg object – tbd)
type: "circle",
size: Math.max(Math.round(Math.random() * 12), 4),
};
}
// send the datum to the chart
chart.datum(obj);
});
// drive data into the chart at average interval of five seconds
// here, set the timeout to roughly five seconds
timeout = Math.round(timeScale(normal()));
// do forever
dataGenerator();
}, timeout);
}
// start the data generator
dataGenerator();
</script>
<!-- Author: Bo Ericsson, bo@boe.net -->
<!-- Inspiration from numerous examples by Mike Bostock, http://bl.ocks.org/mbostock, -->
<!-- and example by Andy Aiken, http://blog.scottlogic.com/2014/09/19/interactive.html -->
'use strict';
function realTimeChartMulti() {
var version = "0.1.0",
datum, data,
maxSeconds = 300, pixelsPerSecond = 10,
svgWidth = 700, svgHeight = 300,
margin = { top: 20, bottom: 20, left: 100, right: 30, topNav: 10, bottomNav: 20 },
dimension = { chartTitle: 20, xAxis: 20, yAxis: 20, xTitle: 20, yTitle: 20, navChart: 70 },
maxY = 100, minY = 0,
chartTitle, yTitle, xTitle,
drawXAxis = true, drawYAxis = true, drawNavChart = true,
border,
selection,
barId = 0,
yDomain = [],
debug = false,
barWidth = 5,
halted = false,
x, y,
xNav, yNav,
width, height,
widthNav, heightNav,
xAxisG, yAxisG,
xAxis, yAxis,
svg;
// create the chart
var chart = function(s) {
selection = s;
if (selection == undefined) {
console.error("selection is undefined");
return;
};
// process titles
chartTitle = chartTitle || "";
xTitle = xTitle || "";
yTitle = yTitle || "";
// compute component dimensions
var chartTitleDim = chartTitle == "" ? 0 : dimension.chartTitle,
xTitleDim = xTitle == "" ? 0 : dimension.xTitle,
yTitleDim = yTitle == "" ? 0 : dimension.yTitle,
xAxisDim = !drawXAxis ? 0 : dimension.xAxis,
yAxisDim = !drawYAxis ? 0 : dimension.yAxis,
navChartDim = !drawNavChart ? 0 : dimension.navChart;
// compute dimension of main and nav charts, and offsets
var marginTop = margin.top + chartTitleDim;
height = svgHeight - marginTop - margin.bottom - chartTitleDim - xTitleDim - xAxisDim - navChartDim + 30;
heightNav = navChartDim - margin.topNav - margin.bottomNav;
var marginTopNav = svgHeight - margin.bottom - heightNav - margin.topNav;
width = svgWidth - margin.left - margin.right;
widthNav = width;
// append the svg
svg = selection.append("svg")
.attr("width", svgWidth)
.attr("height", svgHeight)
.style("border", function(d) {
if (border) return "1px solid lightgray";
else return null;
});
// create main group and translate
var main = svg.append("g")
.attr("transform", "translate (" + margin.left + "," + marginTop + ")");
// define clip-path
main.append("defs").append("clipPath")
.attr("id", "myClip")
.append("rect")
.attr("x", 0)
.attr("y", 0)
.attr("width", width)
.attr("height", height);
// create chart background
main.append("rect")
.attr("x", 0)
.attr("y", 0)
.attr("width", width)
.attr("height", height)
.style("fill", "#f5f5f5");
// note that two groups are created here, the latter assigned to barG;
// the former will contain a clip path to constrain objects to the chart area;
// no equivalent clip path is created for the nav chart as the data itself
// is clipped to the full time domain
var barG = main.append("g")
.attr("class", "barGroup")
.attr("transform", "translate(0, 0)")
.attr("clip-path", "url(#myClip")
.append("g");
// add group for x axis
xAxisG = main.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")");
// add group for y axis
yAxisG = main.append("g")
.attr("class", "y axis");
// in x axis group, add x axis title
xAxisG.append("text")
.attr("class", "title")
.attr("x", width / 2)
.attr("y", 25)
.attr("dy", ".71em")
.text(function(d) {
var text = xTitle == undefined ? "" : xTitle;
return text;
});
// in y axis group, add y axis title
yAxisG.append("text")
.attr("class", "title")
.attr("transform", "rotate(-90)")
.attr("x", - height / 2)
.attr("y", -margin.left + 15) //-35
.attr("dy", ".71em")
.text(function(d) {
var text = yTitle == undefined ? "" : yTitle;
return text;
});
// in main group, add chart title
main.append("text")
.attr("class", "chartTitle")
.attr("x", width / 2)
.attr("y", -20)
.attr("dy", ".71em")
.text(function(d) {
var text = chartTitle == undefined ? "" : chartTitle;
return text;
});
// define main chart scales
x = d3.time.scale().range([0, width]);
y = d3.scale.ordinal().domain(yDomain).rangeRoundPoints([height, 0], 1)
// define main chart axis
xAxis = d3.svg.axis().orient("bottom");
yAxis = d3.svg.axis().orient("left");
// add nav chart
var nav = svg.append("g")
.attr("transform", "translate (" + margin.left + "," + marginTopNav + ")");
// add nav background
nav.append("rect")
.attr("x", 0)
.attr("y", 0)
.attr("width", width)
.attr("height", heightNav)
.style("fill", "#F5F5F5")
.style("shape-rendering", "crispEdges")
.attr("transform", "translate(0, 0)");
// add group to data items
var navG = nav.append("g")
.attr("class", "nav");
// add group to hold nav x axis
// please note that a clip path has yet to be added here (tbd)
var xAxisGNav = nav.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + heightNav + ")");
// define nav chart scales
xNav = d3.time.scale().range([0, widthNav]);
yNav = d3.scale.ordinal().domain(yDomain).rangeRoundPoints([heightNav, 0], 1)
// define nav axis
var xAxisNav = d3.svg.axis().orient("bottom");
// compute initial time domains...
var ts = new Date().getTime();
// first, the full time domain
var endTime = new Date(ts);
var startTime = new Date(endTime.getTime() - maxSeconds * 1000);
var interval = endTime.getTime() - startTime.getTime();
// then the viewport time domain (what's visible in the main chart and the viewport in the nav chart)
var endTimeViewport = new Date(ts);
var startTimeViewport = new Date(endTime.getTime() - width / pixelsPerSecond * 1000);
var intervalViewport = endTimeViewport.getTime() - startTimeViewport.getTime();
var offsetViewport = startTimeViewport.getTime() - startTime.getTime();
// set the scale domains for main and nav charts
x.domain([startTimeViewport, endTimeViewport]);
xNav.domain([startTime, endTime]);
// update axis with modified scale
xAxis.scale(x)(xAxisG);
yAxis.scale(y)(yAxisG);
xAxisNav.scale(xNav)(xAxisGNav);
// create brush (moveable, changable rectangle that determines the time domain of main chart)
var viewport = d3.svg.brush()
.x(xNav)
.extent([startTimeViewport, endTimeViewport])
.on("brush", function () {
// get the current time extent of viewport
var extent = viewport.extent();
startTimeViewport = extent[0];
endTimeViewport = extent[1];
// compute viewport extent in milliseconds
intervalViewport = endTimeViewport.getTime() - startTimeViewport.getTime();
offsetViewport = startTimeViewport.getTime() - startTime.getTime();
// handle invisible viewport
if (intervalViewport == 0) {
intervalViewport = maxSeconds * 1000;
offsetViewport = 0;
}
// update the x domain of the main chart
x.domain(viewport.empty() ? xNav.domain() : extent);
// update the x axis of the main chart
xAxis.scale(x)(xAxisG);
// update display
refresh();
});
// create group and assign to brush
var viewportG = nav.append("g")
.attr("class", "viewport")
.call(viewport)
.selectAll("rect")
.attr("height", heightNav);
// initial invocation; update display
data = [];
refresh();
// function to refresh the viz upon changes of the time domain
// (which happens constantly), or after arrival of new data, or at init
function refresh() {
// process data to remove too late data items
data = data.filter(function(d) {
if (d.time.getTime() > startTime.getTime()) return true;
})
// determine number of categories
var categoryCount = yDomain.length;
if (debug) console.log("yDomain", yDomain)
// here we bind the new data to the main chart
// note: no key function is used here; therefore the data binding is
// by index, which effectivly means that available DOM elements
// are associated with each item in the available data array, from
// first to last index; if the new data array contains fewer elements
// than the existing DOM elements, the LAST DOM elements are removed;
// basically, for each step, the data items "walks" leftward (each data
// item occupying the next DOM element to the left);
// This data binding is very different from one that is done with a key
// function; in such a case, a data item stays "resident" in the DOM
// element, and such DOM element (with data) would be moved left, until
// the x position is to the left of the chart, where the item would be
// exited
var updateSel = barG.selectAll(".bar")
.data(data);
// remove items
updateSel.exit().remove();
// add items
updateSel.enter()
.append(function(d) {
if (debug) { console.log("d", JSON.stringify(d)); }
if (d.type == undefined) console.error(JSON.stringify(d))
var type = d.type || "circle";
var node = document.createElementNS("http://www.w3.org/2000/svg", type);
return node;
})
.attr("class", "bar")
.attr("id", function() {
return "bar-" + barId++;
});
// update items; added items are now part of the update selection
updateSel
.attr("x", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "rect":
var size = d.size || 6;
retVal = Math.round(x(d.time) - size / 2);
break;
default:
}
return retVal;
})
.attr("y", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "rect":
var size = d.size || 6;
retVal = y(d.category) - size / 2;
break;
default:
}
return retVal;
})
.attr("cx", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "circle":
retVal = Math.round(x(d.time));
break;
default:
}
return retVal;
})
.attr("cy", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "circle":
retVal = y(d.category);
break;
default:
}
return retVal;
})
.attr("r", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "circle":
retVal = d.size / 2;
break;
default:
}
return retVal;
})
.attr("width", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "rect":
retVal = d.size;
break;
default:
}
return retVal;
})
.attr("height", function(d) {
var retVal = null;
switch (getTagName(this)) {
case "rect":
retVal = d.size;
break;
default:
}
return retVal;
})
.style("fill", function(d) { return d.color || "black"; })
//.style("stroke", "orange")
//.style("stroke-width", "1px")
//.style("stroke-opacity", 0.8)
.style("fill-opacity", function(d) { return d.opacity || 1; });
// create update selection for the nav chart, by applying data
var updateSelNav = navG.selectAll("circle")
.data(data);
// remove items
updateSelNav.exit().remove();
// add items
updateSelNav.enter().append("circle")
.attr("r", 1)
.attr("fill", "black")
// added items now part of update selection; set coordinates of points
updateSelNav
.attr("cx", function(d) {
return Math.round(xNav(d.time));
})
.attr("cy", function(d) {
return yNav(d.category);
})
} // end refreshChart function
function getTagName(that) {
var tagName = d3.select(that).node().tagName;
return (tagName);
}
// function to keep the chart "moving" through time (right to left)
setInterval(function() {
if (halted) return;
// get current viewport extent
var extent = viewport.empty() ? xNav.domain() : viewport.extent();
var interval = extent[1].getTime() - extent[0].getTime();
var offset = extent[0].getTime() - xNav.domain()[0].getTime();
// compute new nav extents
endTime = new Date();
startTime = new Date(endTime.getTime() - maxSeconds * 1000);
// compute new viewport extents
startTimeViewport = new Date(startTime.getTime() + offset);
endTimeViewport = new Date(startTimeViewport.getTime() + interval);
viewport.extent([startTimeViewport, endTimeViewport])
// update scales
x.domain([startTimeViewport, endTimeViewport]);
xNav.domain([startTime, endTime]);
// update axis
xAxis.scale(x)(xAxisG);
xAxisNav.scale(xNav)(xAxisGNav);
// refresh svg
refresh();
}, 200)
// end setInterval function
return chart;
} // end chart function
// chart getters/setters
// new data item (this most recent item will appear
// on the right side of the chart, and begin moving left)
chart.datum = function(_) {
if (arguments.length == 0) return datum;
datum = _;
data.push(datum);
return chart;
}
// svg width
chart.width = function(_) {
if (arguments.length == 0) return svgWidth;
svgWidth = _;
return chart;
}
// svg height
chart.height = function(_) {
if (arguments.length == 0) return svgHeight;
svgHeight = _;
return chart;
}
// svg border
chart.border = function(_) {
if (arguments.length == 0) return border;
border = _;
return chart;
}
// chart title
chart.title = function(_) {
if (arguments.length == 0) return chartTitle;
chartTitle = _;
return chart;
}
// x axis title
chart.xTitle = function(_) {
if (arguments.length == 0) return xTitle;
xTitle = _;
return chart;
}
// y axis title
chart.yTitle = function(_) {
if (arguments.length == 0) return yTitle;
yTitle = _;
return chart;
}
// yItems (can be dynamically added after chart construction)
chart.yDomain = function(_) {
if (arguments.length == 0) return yDomain;
yDomain = _;
if (svg) {
// update the y ordinal scale
y = d3.scale.ordinal().domain(yDomain).rangeRoundPoints([height, 0], 1);
// update the y axis
yAxis.scale(y)(yAxisG);
// update the y ordinal scale for the nav chart
yNav = d3.scale.ordinal().domain(yDomain).rangeRoundPoints([heightNav, 0], 1);
}
return chart;
}
// debug
chart.debug = function(_) {
if (arguments.length == 0) return debug;
debug = _;
return chart;
}
// halt
chart.halt = function(_) {
if (arguments.length == 0) return halted;
halted = _;
return chart;
}
// version
chart.version = version;
return chart;
} // end realTimeChart function
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toklok Dec 7, 2016

So very amazing! I am still always learning so seeing a component that can connect real time data and time is a treasure! I appreciate you publishing this to the world for people to learn from!

toklok commented Dec 7, 2016

So very amazing! I am still always learning so seeing a component that can connect real time data and time is a treasure! I appreciate you publishing this to the world for people to learn from!

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aaronkyle Jul 3, 2018

This is really great. Any chance you'd be willing to port this over to Mike's new project, Observable HQ?

aaronkyle commented Jul 3, 2018

This is really great. Any chance you'd be willing to port this over to Mike's new project, Observable HQ?

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AF7TI Sep 5, 2018

Use d3.timer to make x axis transitions smooth. See discussion here d3/d3-axis#23 (comment)

Here's an example I made (requires my dev socket server to be up) https://bl.ocks.org/AF7TI/915b411c47cca8290db08f971dd02979

AF7TI commented Sep 5, 2018

Use d3.timer to make x axis transitions smooth. See discussion here d3/d3-axis#23 (comment)

Here's an example I made (requires my dev socket server to be up) https://bl.ocks.org/AF7TI/915b411c47cca8290db08f971dd02979

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