What is "peaks" in tutorialApp?

I am learning Matlab graphical user interface tools. I find that tutorialApp.mlapp seems to be a readily available thing, embedded in Matlab itself. I have successfully run it. Now, looking at the code, I would like to understand it better and play with it some. These lines (16-18) seem to be doing the hard work of building the graph:

value = app.AmplitudeSlider.Value;
plot(app.UIAxes, value*peaks)
app.UIAxes.YLim = [-1000 1000];

Okay, so it would appear that the data must be contained in this object called peaks. But I can't find that object defined anywhere. Where is it, and what is its type? Or if I'm wrong, where is the data, really?

[Dyuman Joshi]

"Where is it, and what is its type? Or if I'm wrong, where is the data, really?"

As Voss has mentioned, it is a built-in function, i.e. it comes with MATLAB.

You can use the MATLAB Documentation to search for such functions, either online or on your MATLAB app using help like this -

help peaks

 PEAKS  A sample function of two variables.
    PEAKS is a function of two variables, obtained by translating and
    scaling Gaussian distributions, which is useful for demonstrating
    MESH, SURF, PCOLOR, CONTOUR, etc.
    There are several variants of the calling sequence:
 
        Z = PEAKS;
        Z = PEAKS(N);
        Z = PEAKS(V);
        Z = PEAKS(X,Y);
 
        PEAKS;
        PEAKS(N);
        PEAKS(V);
        PEAKS(X,Y);
 
        [X,Y,Z] = PEAKS;
        [X,Y,Z] = PEAKS(N);
        [X,Y,Z] = PEAKS(V);
 
    The first variant produces a 49-by-49 matrix.
    The second variant produces an N-by-N matrix.
    The third variant produces an N-by-N matrix where N = length(V).
    The fourth variant evaluates the function at the given X and Y,
    which must be the same size.  The resulting Z is also that size.
 
    The next four variants, with no output arguments, do a SURF
    plot of the result.
 
    The last three variants also produce two matrices, X and Y, for
    use in commands such as PCOLOR(X,Y,Z) or SURF(X,Y,Z,DEL2(Z)).
 
    If not given as input, the underlying matrices X and Y are
        [X,Y] = MESHGRID(V,V) 
    where V is a given vector, or V is a vector of length N with
    elements equally spaced from -3 to 3.  If no input argument is
    given, the default N is 49.

    Documentation for peaks
       doc peaks

Answer 1

[Voss]

peaks is a built-in function:

https://www.mathworks.com/help/matlab/ref/peaks.html

[Voss]

@Ken: Did this answer clarify the problem? If so, please Accept it.

Answer 2

[Image Analyst]

peaks a built-in function that you can actually open up and look at in the editor. Do this at the command line:

>> edit peaks.m