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DynamicPlot: An example of handle semantics with MATLAB classes

version 1.0.0.1 (5.51 KB) by Gautam Vallabha
A MATLAB class that implements an automatically-updated display with pause and resume.

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Updated 01 Sep 2016

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obj = dynamicplot(genFcn, T)
creates a figure that is automatically updated (by calling a generator function genFcn) every T seconds. obj is a handle to the created object.

E.g.: d = dynamicplot(@() randn(1,100), 0.5);
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The DYNAMICPLOT class demonstrates how to get reference (aka. handle) semantics using MATLAB classes. Typically when one modifies a MATLAB object, it needs be returned to the caller:
obj = set(obj, 'myParameter', 10.0);
But with handle semantics, you can simply do this:
set(obj, 'myParameter', 10.0);

Handle semantics is especially useful with objects that need to be updated autonomously (e.g., acquiring data from a data aquisition device or an instrument).

The handle semantics were accomplished as follows.
(1) the constructor defines the instance variables and
(2) returns a set of function handles to access these instance variables.
(3) Other methods use only the function handles to access and modify the data.

Detailed example of handle semantics:

d = dynamicplot(@() randn(1,100), 0.5);
getdata(d) % try this several times
setUpdatePeriod(d, 0.2)
getNumUpdates(d) % try several times
setLineStyle(d,'color','r');

% Object assignment respects the
% handle semantics. d and d2 refer
% to the same object.
d2 = d;
pauseDisplay(d);
resumeDisplay(d2);

% Validity checks can be built into
% the object itself
delete(d);
getdata(d) % will generate an error
getdata(d2) % generates error also

% It is possible to have multiple
% objects without any clashes

d1 = dynamicplot(@() randn(1,100), 0.1);
d2 = dynamicplot(@() rand(1,100), 0.1);
pauseDisplay(d1);
getNumUpdates(d1)
getNumUpdates(d2)
resumeDisplay(d1);
delete(d1);

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NOTE: The primary purpose of the DYNAMICPLOT class is to demonstrate how to get handle semantics with MATLAB classes. Feel free to improve or extend the functionality.

Comments and Ratings (1)

Yi Cao

A nice tool and a clever idea to explore what MATLAB can do.

Updates

1.0.0.1

Updated license

MATLAB Release Compatibility
Created with R2007b
Compatible with any release
Platform Compatibility
Windows macOS Linux

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