ChartDirector 7.0 (ASP/COM/VB Edition)

Simple Real-Time Chart (Web)

This sample program demonstrates a real-time chart with configurable chart update rate, in which the chart image is updated via streaming.

The chart is updated by calling JsChartViewer.streamUpdate on the browser side. This method sends a "stream update request" to the server to update the chart image. The charting code in the server always draws the chart using the most updated data. By using a timer to call JsChartViewer.streamUpdate periodically, we can get a real time chart.

On the server side, WebChartViewer.IsStreamRequest is used to determine if the request is a normal request or is a stream update request. In the latter case, WebChartViewer.streamChart is used to stream the updated chart to the browser and the script terminates immediately.

Note that the streaming method used in this example only updates the chart image, but not the image map or the Javascript Chart Model, so the chart does not have tooltips or track cursor features. See Real-Time Chart with Track Line (Web) for an alternative method that can support tooltips and track cursors.

Source Code Listing

[Web Version (in ASP)] aspdemo\realtimedemo.asp
<%@ language="vbscript" %> <% Set cd = CreateObject("ChartDirector.API") ' ' Data to draw the chart. In this demo, the data buffer will be filled by a random data generator. ' In real life, the data is probably stored in a buffer (eg. a database table, a text file, or some ' global memory) and updated by other means. ' ' We use a data buffer to emulate the last 240 samples. sampleSize = 240 ReDim dataSeries1(sampleSize - 1) ReDim dataSeries2(sampleSize - 1) ReDim dataSeries3(sampleSize - 1) ReDim timeStamps(sampleSize - 1) ' Our pseudo random number generator firstDate = DateAdd("s", -(UBound(timeStamps) + 1), Now) For i = 0 To UBound(timeStamps) timeStamps(i) = DateAdd("s", i, firstDate) p = Second(timeStamps(i)) + Minute(timeStamps(i)) * 60 + Hour(timeStamps(i)) * 3600 dataSeries1(i) = Cos(p * 2.1) * 10 + 1 / (Cos(p) * Cos(p) + 0.01) + 20 dataSeries2(i) = 100 * Sin(p / 27.7) * Sin(p / 10.1) + 150 dataSeries3(i) = 100 * Cos(p / 6.7) * Cos(p / 11.9) + 150 Next ' Create an XYChart object 600 x 270 pixels in size, with light grey (f4f4f4) background, black ' (000000) border, 1 pixel raised effect, and with a rounded frame. Set c = cd.XYChart(600, 270, &Hf4f4f4, &H000000, 0) Call c.setRoundedFrame() ' Set the plotarea at (55, 62) and of size 520 x 175 pixels. Use white (ffffff) background. Enable ' both horizontal and vertical grids by setting their colors to grey (cccccc). Set clipping mode to ' clip the data lines to the plot area. Call c.setPlotArea(55, 62, 520, 175, &Hffffff, -1, -1, &Hcccccc, &Hcccccc) Call c.setClipping() ' Add a title to the chart using 15pt Times New Roman Bold Italic font, with a light grey (dddddd) ' background, black (000000) border, and a glass like raised effect. Call c.addTitle("Field Intensity at Observation Satellite", "Times New Roman Bold Italic", 15 _ ).setBackground(&Hdddddd, &H000000, cd.glassEffect()) ' Add a legend box at the top of the plot area with 9pt Arial Bold font. We set the legend box to ' the same width as the plot area and use grid layout (as opposed to flow or top/down layout). This ' distributes the 3 legend icons evenly on top of the plot area. Set b = c.addLegend2(55, 33, 3, "Arial Bold", 9) Call b.setBackground(cd.Transparent, cd.Transparent) Call b.setWidth(520) ' Configure the y-axis with a 10pt Arial Bold axis title Call c.yAxis().setTitle("Intensity (V/m)", "Arial Bold", 10) ' Configure the x-axis to auto-scale with at least 75 pixels between major tick and 15 pixels ' between minor ticks. This shows more minor grid lines on the chart. Call c.xAxis().setTickDensity(75, 15) ' Set the axes width to 2 pixels Call c.xAxis().setWidth(2) Call c.yAxis().setWidth(2) ' Set the x-axis label format Call c.xAxis().setLabelFormat("{value|hh:nn:ss}") ' Create a line layer to plot the lines Set layer = c.addLineLayer2() ' The x-coordinates are the timeStamps. Call layer.setXData(timeStamps) ' The 3 data series are used to draw 3 lines. Here we put the latest data values as part of the data ' set name, so you can see them updated in the legend box. Call layer.addDataSet(dataSeries1, &Hff0000, c.formatValue(dataSeries1(UBound(dataSeries1)), _ "Alpha: <*bgColor=FFCCCC*> {value|2} ")) Call layer.addDataSet(dataSeries2, &H00cc00, c.formatValue(dataSeries2(UBound(dataSeries2)), _ "Beta: <*bgColor=CCFFCC*> {value|2} ")) Call layer.addDataSet(dataSeries3, &H0000ff, c.formatValue(dataSeries3(UBound(dataSeries3)), _ "Gamma: <*bgColor=CCCCFF*> {value|2} ")) ' Output the chart Set viewer = cd.WebChartViewer(Request, "chart1") Call viewer.setChart(c, cd.SVG) ' Check if is a stream request to update the chart If viewer.IsStreamRequest Then ' Stream the updated chart to the browser Call viewer.streamChart(Response) Call Response.End End If %> <!DOCTYPE html> <html> <head> <title>Simple Real-Time Chart</title> <script type="text/javascript" src="cdjcv.js"></script> </head> <body style="margin:0px"> <table cellspacing="0" cellpadding="0" border="0"> <tr> <td align="right" colspan="2" style="background:#000088; color:#ffff00; padding:0px 4px 2px 0px;"> <a style="color:#FFFF00; font:italic bold 10pt Arial; text-decoration:none" href=""> Advanced Software Engineering </a> </td> </tr> <tr valign="top"> <td style="width:130px; background:#c0c0ff; border-right:black 1px solid; border-bottom:black 1px solid;"> <br /> <br /> <div style="font:12px Verdana; padding:10px;"> <b>Update Period</b><br /> <select id="UpdatePeriod" style="width:110px"> <option value="5">5</option> <option value="10" selected="selected">10</option> <option value="20">20</option> <option value="30">30</option> <option value="60">60</option> </select> <br /><br /><br /> <b>Time Remaining</b><br /> <div style="width:108px; border:#888888 1px inset;"> <div style="margin:3px" id="TimeRemaining">0</div> </div> </div> </td> <td> <div style="font: bold 20pt Arial; margin:5px 0px 0px 5px;"> Simple Real-Time Chart </div> <hr style="border:solid 1px #000080" /> <div style="padding:0px 5px 5px 10px"> <!-- ****** Here is the chart image ****** --> <%=viewer.renderHTML()%> </div> </td> </tr> </table> <script type="text/javascript"> // // Executes once every second to update the countdown display. Updates the chart when the countdown reaches 0. // function timerTick() { // Get the update period and the time left var updatePeriod = parseInt(document.getElementById("UpdatePeriod").value); var timeLeft = Math.min(parseInt(document.getElementById("TimeRemaining").innerHTML), updatePeriod) - 1; if (timeLeft == 0) // Can update the chart now JsChartViewer.get('<%=viewer.Id%>').streamUpdate(); else if (timeLeft < 0) // Reset the update period timeLeft += updatePeriod; // Update the countdown display document.getElementById("TimeRemaining").innerHTML = timeLeft; } window.setInterval("timerTick()", 1000); </script> </body> </html>