2e:null 2f:["$","title",null,{"children":"D3 Real Time Chart with Multiple Data Streams | Aaron Kyle Dennis | Observable"}] 34:T91d,md` 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](http://bl.ocks.org/boeric/6a83de20f780b42fadb9), Repos: GitHub Gist [here](https://gist.github.com/boeric/6a83de20f780b42fadb9), GitHub [here](https://github.com/boeric/d3RealTimeChartMulti). The component is a derivative of [D3 Based Real Time Chart](http://bl.ocks.org/boeric/3b57a788a4b96e1af211/). The component adheres to the pattern described in [Towards Reusable Chart](http://bost.ocks.org/mike/chart/). `35:Td58,chart={ //'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(); }36:T3fe6, //'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 function37:[] 32:{"id":"6eb44fa396bd44a2","slug":"d3-real-time-chart-with-multiple-data-streams","title":"D3 Real Time Chart with Multiple Data Streams","thumbnail":"ef2cebf40af12fcc0ae4b0fee728125108a7d847c39aa82820b6d543fc5fa2b6","access_level":"public","create_time":"$D2018-07-03T12:26:22.303Z","update_time":"$D2018-07-03T12:55:17.425Z","view_time":null,"first_public_time":"$D2018-07-03T12:51:12.544Z","has_unpublished_edits":null,"fork":false,"stars":36,"starred":false,"owner":{"type":"team","id":"8d652a601386fcf4","login":"aaronkyle","name":"Aaron Kyle Dennis","avatar_url":"https://avatars-next.observableusercontent.com/eb6d0b32ccc6c8febbf105ce4d2a938819bcbd1c6a2c108d3a9c01745d3590f2","tier":"starter_2024"},"version":69,"publish_version":69,"role":null,"authored":false,"authors":[{"type":"individual","id":"a7fa3027921865cf","login":"aaronkyle","name":"Aaron Kyle Dennis","avatar_url":"https://avatars-next.observableusercontent.com/eb6d0b32ccc6c8febbf105ce4d2a938819bcbd1c6a2c108d3a9c01745d3590f2","tier":null}],"members":[{"type":"individual","id":"a7fa3027921865cf","login":"aaronkyle","name":"Aaron Kyle Dennis","avatar_url":"https://avatars-next.observableusercontent.com/eb6d0b32ccc6c8febbf105ce4d2a938819bcbd1c6a2c108d3a9c01745d3590f2","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":28,"collection":{"id":"7cbfafa649b21931","slug":"ports","title":"Ports","owner":{"id":"8d652a601386fcf4","login":"aaronkyle","name":"Aaron Kyle Dennis"}},"type":"notebook","body":{"title":"D3 Real Time Chart with Multiple Data Streams","cells":[{"id":0,"value":"md`# D3 Real Time Chart with Multiple Data Streams`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":2,"value":"md`This post ports to Observabele [Bo Ericsson](https://bl.ocks.org/boeric)’s [Block 6a83de20f780b42fadb9](https://bl.ocks.org/boeric/6a83de20f780b42fadb9).`\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"div = html`

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