What is a handle?

I always see the word 'handle' in the matlab community but I don't quite understand what is it even I search it online. I am an absolute begineer of matlab, can anyone please give me a simple explaination or direct me to the right resource. Thank you.

Answer 1

[Steven Lord]

What's the context in which you see that term? There are at least three different meanings for that term, though two of them are somewhat related.

• Handle as related to graphics? Start with this documentation page. Graphics handles let you manipulate graphics objects on screen; for example if I have a line's handle I can change its Color property and so change what color it is.

h = plot(1:10, 1:10); % h is the line's handle. By default it is blue.

figure % Let's make a second line so you can see the difference when I change its color
h2 = plot(1:10, 1:10);
h2.Color = 'r'; % Let's make this line red

• Handle in terms of object-oriented programming? See here, though this is often thought of as an advanced skill for MATLAB programming. Graphics handles are handle objects, though not all handle objects are graphics objects.
• Handle as related to evaluating a function, like with an ODE solver or optimization routine? Those are function handles, which are useful in passing a "reference" to function A into function B so that function B can call function A with input arguments of its choice.

f = @sin;

Find a zero of the function y = sin(x). Start looking at 1. fzero will call f with points of its choosing as it looks for a solution.

x = fzero(f, 1) 

x = 1.5485e-24

To check, evaluate the function handle yourself at the point fzero found.

shouldBeCloseTo0 = f(x)

shouldBeCloseTo0 = 1.5485e-24

That's pretty close to 0.

[Cheuk Yin Wong]

Thank you very much! This is very clear.