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D3 Based Real Time Chart
Raw
README.md

D3 Based Real Time Chart

The real time chart is a resuable Javascript component that accepts real time data. The chart's time domain is moving with the passage of time, which means that any data placed in the chart eventually will age out and leave the chart. In addition to the main chart, the component also manages a "focus" window with a viewport (d3.brush) that can moved and sized to view an arbitrary portion of the time series data.

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

The following options are currently supported:

  • width and height in pixels (Number)
  • border (Boolean)
  • title, xTitle, yTitle (String)
  • barWidth in pixels (Number)

Future options will include:

  • Scale domain of real time data (currently a domain of [0, 100] is assumed for the y scale)
  • Use of SVG rects, circles, paths etc. to represent data (in addition to bars)

Use the component like so:

// create the real time chart
var chart = realTimeChart()
    .title("Chart Title")
    .yTitle("Y Scale")
    .xTitle("X Scale")
    .border(true)
    .width(600)
    .height(290)
    .barWidth(1)
    .initialData(data);

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

// create new data item and inject into chart
var now = new Date();
var obj = {
  value: 50
  time: now,
  color: "red",
  ts: now.getTime(),
  interval: timeout
};

// send the datum to the chart
chart.datum(obj);
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index.html
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<!-- Author: Bo Ericsson -->
<title>Real Time Chart</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">
<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: 600px; max-height: 400px; padding: 10px">
<div class="well">
<h4>D3 Based Real Time Chart
</div>
<div id="viewDiv"></div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js"></script>
<script src="realTimeChart.js"></script>
<script>
'use strict';
// mean and deviation for time interval
var meanMs = 1000, // milliseconds
dev = 150;
// define time scale
var timeScale = d3.scale.linear()
.domain([300, 1700])
.range([300, 1700])
.clamp(true);
// define value scale
var valueScale = d3.scale.linear()
.domain([0, 1])
.range([30, 95]);
// generate initial data
var normal = d3.random.normal(1000, 150);
var currMs = new Date().getTime() - 300000 - 4000;
var data = d3.range(300).map(function(d, i, arr) {
var value = valueScale(Math.random()); // random data
//var value = Math.round((d % 60) / 60 * 95); // ramp data
var interval = Math.round(timeScale(normal()));
currMs += interval;
var time = new Date(currMs);
var obj = { interval: interval, value: value, time: time, ts: currMs }
return obj;
})
// create the real time chart
var chart = realTimeChart()
.title("Chart Title")
.yTitle("Y Scale")
.xTitle("X Scale")
.border(true)
.width(600)
.height(290)
.barWidth(1)
.initialData(data);
console.log("Version: ", chart.version);
console.dir("Dir++");
console.trace();
console.warn("warn")
// invoke the chart
var chartDiv = d3.select("#viewDiv").append("div")
.attr("id", "chartDiv")
.call(chart);
// alternative invocation
//chart(chartDiv);
// drive data into the chart roughly every second
// in a normal use case, real time data would arrive through the network or some other mechanism
var d = 0;
function dataGenerator() {
var timeout = Math.round(timeScale(normal()));
setTimeout(function() {
// create new data item
var now = new Date();
var obj = {
value: valueScale(Math.random()), // random data
//value: Math.round((d++ % 60) / 60 * 95), // ramp data
time: now,
color: "red",
ts: now.getTime(),
interval: timeout
};
// send the datum to the chart
chart.datum(obj);
// do forever
dataGenerator();
}, timeout);
}
// start the data generator
dataGenerator();
</script>
Raw
realTimeChart.js
<!-- 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 realTimeChart() {
var version = "0.1.0",
datum, initialData, data,
maxSeconds = 300, pixelsPerSecond = 10,
svgWidth = 700, svgHeight = 300,
margin = { top: 20, bottom: 20, left: 50, right: 30, topNav: 10, bottomNav: 20 },
dimension = { chartTitle: 20, xAxis: 20, yAxis: 20, xTitle: 20, yTitle: 20, navChart: 70 },
barWidth = 3,
maxY = 100, minY = 0,
chartTitle, yTitle, xTitle,
drawXAxis = true, drawYAxis = true, drawNavChart = true,
border,
selection,
barId = 0;
// 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;
var xTitleDim = xTitle == "" ? 0 : dimension.xTitle;
var yTitleDim = yTitle == "" ? 0 : dimension.yTitle;
var xAxisDim = !drawXAxis ? 0 : dimension.xAxis;
var yAxisDim = !drawYAxis ? 0 : dimension.yAxis;
var navChartDim = !drawNavChart ? 0 : dimension.navChart;
// compute chart dimension and offset
var marginTop = margin.top + chartTitleDim;
var height = svgHeight - marginTop - margin.bottom - chartTitleDim - xTitleDim - xAxisDim - navChartDim + 30;
var heightNav = navChartDim - margin.topNav - margin.bottomNav;
var marginTopNav = svgHeight - margin.bottom - heightNav - margin.topNav;
var width = svgWidth - margin.left - margin.right;
var widthNav = width;
// append the svg
var 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
var xAxisG = main.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")");
// add group for y axis
var 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", -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
var x = d3.time.scale().range([0, width]);
var y = d3.scale.linear().domain([minY, maxY]).range([height, 0]);
// define main chart axis
var xAxis = d3.svg.axis().orient("bottom");
var 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 hold line and area paths
var navG = nav.append("g")
.attr("class", "nav");
// add group to hold nav x axis
var xAxisGNav = nav.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + heightNav + ")");
// define nav scales
var xNav = d3.time.scale().range([0, widthNav]);
var yNav = d3.scale.linear().domain([minY, maxY]).range([heightNav, 0]);
// define nav axis
var xAxisNav = d3.svg.axis().orient("bottom");
// define function that will draw the nav area chart
var navArea = d3.svg.area()
.x(function (d) { return xNav(d.time); })
.y1(function (d) { return yNav(d.value); })
.y0(heightNav);
// define function that will draw the nav line chart
var navLine = d3.svg.line()
.x(function (d) { return xNav(d.time); })
.y(function (d) { return yNav(d.value); });
// 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];
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
data = initialData || [];
// update display
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 or too early data items
// (the latter could occur if the chart is stopped, while data
// is being pumped in)
data = data.filter(function(d) {
if (d.time.getTime() > startTime.getTime() &&
d.time.getTime() < endTime.getTime())
return true;
})
// 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();
// append items
updateSel.enter().append("rect")
.attr("class", "bar")
.attr("id", function() {
return "bar-" + barId++;
})
.attr("shape-rendering", "crispEdges");
// update items
updateSel
.attr("x", function(d) { return Math.round(x(d.time) - barWidth); })
.attr("y", function(d) { return y(d.value); })
.attr("width", barWidth)
.attr("height", function(d) { return height - y(d.value); })
.style("fill", function(d) { return d.color == undefined ? "black" : d.color; })
//.style("stroke", "none")
//.style("stroke-width", "1px")
//.style("stroke-opacity", 0.5)
.style("fill-opacity", 1);
// also, bind data to nav chart
// first remove current paths
navG.selectAll("path").remove();
// then append area path...
navG.append('path')
.attr('class', 'area')
.attr('d', navArea(data));
// ...and line path
navG.append('path')
.attr('class', 'line')
.attr('d', navLine(data));
} // end refreshChart function
// function to keep the chart "moving" through time (right to left)
setInterval(function() {
// 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 getter/setters
// array of inital data
chart.initialData = function(_) {
if (arguments.length == 0) return initialData;
initialData = _;
return chart;
}
// 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;
}
// bar width
chart.barWidth = function(_) {
if (arguments.length == 0) return barWidth;
barWidth = _;
return chart;
}
// version
chart.version = version;
return chart;
} // end realTimeChart function
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