update

Class: matlab.graphics.chartcontainer.ChartContainer
Package: matlab.graphics.chartcontainer

Update instance of chart container subclass after setting properties

Since R2019b

Syntax

update(obj)


Description

update(obj) updates the contents of the chart after one or more property values change. Define this method to update the underlying graphics objects in the chart using the new property values. This method executes during the next drawnow execution, after the user changes one or more property values on the chart.

Input Arguments

obj — Object of the class

chart object

Object of the class that inherits from the matlab.graphics.chartcontainer.ChartContainer base class.

Attributes

Abstract	true
Protected	true

To learn about attributes of methods, see Method Attributes.

Examples

Smooth Line Plot

Define a class called SmoothPlot that plots a set of data using a dotted blue line with a smoothed version of the line.

To define the class, create a file called SmoothPlot.m that contains the following class definition with these features:

• XData and YData public properties that store the x- and y-coordinate data for the original line.

• SmoothColor and SmoothWidth public properties that control the color and width of the smooth line.

• OriginalLine and SmoothLine private properties that store the Line objects for original and smoothed data.

• A setup method that initializes OriginalLine and SmoothLine.

• An update method that updates the plot when the user changes the value of a property.

• A createSmoothData method that calculates a smoothed version of YData.

classdef SmoothPlot < matlab.graphics.chartcontainer.ChartContainer
    properties
        XData (1,:) double = NaN
        YData (1,:) double = NaN
        SmoothColor (1,3) double {mustBeGreaterThanOrEqual(SmoothColor,0),...
            mustBeLessThanOrEqual(SmoothColor,1)} = [0.9290 0.6940 0.1250]
        SmoothWidth (1,1) double = 2
    end
    properties(Access = private,Transient,NonCopyable)
        OriginalLine (1,1) matlab.graphics.chart.primitive.Line
        SmoothLine (1,1) matlab.graphics.chart.primitive.Line
    end
    
    methods(Access = protected)
        function setup(obj)
            % Create the axes
            ax = getAxes(obj);
            
            % Create the original and smooth lines
            obj.OriginalLine = plot(ax,NaN,NaN,'LineStyle',':');
            hold(ax,'on')
            obj.SmoothLine = plot(ax,NaN,NaN);
            hold(ax,'off')
        end
        function update(obj)
            % Update line data
            obj.OriginalLine.XData = obj.XData;
            obj.OriginalLine.YData = obj.YData;
            obj.SmoothLine.XData = obj.XData;
            obj.SmoothLine.YData = createSmoothData(obj);
            
            % Update line color and width
            obj.SmoothLine.Color = obj.SmoothColor;
            obj.SmoothLine.LineWidth = obj.SmoothWidth;
        end
        function sm = createSmoothData(obj)
            % Calculate smoothed data
            v = ones(1,10)*0.1;
            sm = conv(obj.YData,v,'same');
        end
    end
end

Next, create a pair of x and y vectors. Plot x and y by calling the SmoothPlot constructor method, which is provided by the ChartContainer class. Specify the 'XData' and 'YData' name-value pair arguments and return the object as c.

x = 1:1:100;
y = 10*sin(x./5) + 8*sin(10.*x + 0.5);
c = SmoothPlot('XData',x,'YData',y);

Use c to change the color of the smooth line to red.

c.SmoothColor = [1 0 0];

Tips

Avoid calling drawnow within the setup and update methods of your chart class. Calling drawnow in the setup and update methods can cause extraneous updates within your chart, leading to visual flickering and extraneous updates to objects outside your chart, which will negatively impact performance.

Version History

Introduced in R2019b