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POMATLAB - best way to dynamically update a line handles' XData and YData?
 

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    <p>I am collecting data and plotting that data in real time. The data are produced by a motion capture system. I have one class <code>DynamicDataset</code> that is just a wrapper around a 2-column matrix (although it's more nuanced than that) with an event notifier for new data added; another class <code>DynamicPlotter</code> that listens for the data-added event and updates the plot dynamically. Appropriate code snippets:</p> <pre><code>classdef DynamicDataset &lt; handle properties newestData = []; data = [] end events DataAdded end methods function append(obj, val) obj.data(end+1,:) = val; obj.newestData = val; notify(obj, 'DataAdded'); end end end classdef DynamicPlotter &lt; dynamicprops properties FH %# figure handle AH %# axes handle LH %# array of line handles - may have multiple lines on the plot dynProps = {} %# cell array of dynamic property names - %# use to access individual datasets end methods function obj = DynamicPlotter(props) %# props is a cell array of dynamic %# properties to store information for i = 1:length(props) addprop(obj, props{i}); obj.(props{i}) = DynamicDataset; obj.dynProps = [obj.dynProps props{i}]; addlistener(obj.(props{i}), 'DataAdded', @obj.updatePlot(i)); end obj.createBlankPlot(); end function createBlankPlot(obj) obj.FH = figure; obj.AH = axes; hold all; for i = 1:length(obj.dynProps) obj.LH(i) = plot(nan); %# only used to produce a line handle set(obj.LH(i), 'XData', [], 'YData', []); end end function updatePlot(obj, propNum) X = get(obj.LH(propNum), 'XData'); Y = get(obj.LH(propNum), 'YData'); X(end+1) = obj.(dynProps{propNum}).newestData(1); Y(end+1) = obj.(dynProps{propNum}).newestData(2); set(obj.LH(propNum), 'XData', X, 'YData', Y); end end end </code></pre> <p>Based on the MATLAB Code Profile, the <code>set</code> command in <code>updatePlot()</code> is rather expensive. I am wondering if there is a better way to plot individual points as they come? Ideally I would push the single point into <code>XData</code> and <code>YData</code> and draw that point only, but I don't know if this is possible.</p> <p>Please note that there may be multiple lineseries objects (i.e., multiple graphs on the same plot); <code>plot()</code> takes an axes handle as an argument, so it wouldn't consider the properties of the previously drawn line handles (or is there a way to make it do so?); I thought of just doing <code>plot(x,y);hold all;</code> but that would give me separate line handles every time, each corresponding to a single point.</p> <p>It might be that there's no way to make plotting incoming points any faster, but I figured I'd ask.</p> <p><strong>EDIT</strong>: Updated OP with actual code I'm working with, rather than using a generic example that's up for misinterpretation.</p>
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    1. COI don't know if you've seen this but take a look at http://stackoverflow.com/questions/1693429/matlab-oop-is-it-slow-or-am-i-doing-something-wrong . Basically using classes in matlab generally results in poor performance
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    2. COthanks, I have seen that before. My project requires the use of classes for reasons I won't get into, so there isn't any way around that.. but would the `set` call be slow simply because it's called inside a method?
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    3. CO@strictlyrude27: you should correct the addlistener line as: `addlistener(obj.(props{i}), 'DataAdded', @(src,ev) obj.updatePlot(i));`. You also might wanna add `drawnow` at the end of the `updatePlot` function
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