Passing parameters to plot() and axes() functions?

I would like to make a function that adds functionality on top of plot. I.e. a specialized plot. Say,

function my_plot(varargin)
  plot(varargin{1}, varargin{2}, 'r');
  axis square;
end

When calling this, I might like to pass additional parameters:

my_plot(x, y, 'title', 'Hello');

Now, I could do this by explicitly capturing each passed parameter, but this quickly become tedious. I would rather pass a generic array ala the snip below, where parameter/value pairs are simply relayed directly to the plot function:

PlotOpts.LineStyle = '-.';
PlotOpts.Color = [0 1 0];
plot(rand(10,1),PlotOpts);

However, after some fudging around, I did not find a similar way of using axes ala:

h = axes();
AxesOpts.XLabel = 'Real';
AxesOpts.XLim = [0 1];
set(h, AxesOpts);

Answer 1

[Stephen23]

Simple option: use varargin:

function myplot(X,Y,varargin)
plot(X, Y, 'r', varargin{:})

More complex option: convert options struct to cell array:

function myplot(X,Y,S)
C = reshape(fieldnames(S),1,[]);
C(2,:) = struct2cell(S);
plot(X, Y, 'r', C{:})

See:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

I wrote explicit argument names for X and Y for this reason:

https://www.mathworks.com/matlabcentral/answers/364334-naming-variables-wit-using-varargin#comment_499650

[Noah Tang]

What about the situation where only a portion of my_plot 's varargin should be passed to the inner function, say, plot?

For example, I'd like that my function have similiar syntax as plot:

drawEllipse(PDMatrix, center)

drawEllipse(PDMatrix, center, LineSpec)

drawEllipse(__, LineSpec)

drawEllipse(ax, __)

How should I implement this?

[Stephen23]

"How should I implement this?"

Identify the portions that you want to pass to PLOT(), and only pass those to PLOT(). Note that you can use indexing when creating a comma-separated list.

[Noah Tang]

The last syntax where an axes object is passed first seems to make this more complicated for me, do I need an input argument list parser?

[Stephen23]

If your function has one leading optional input it could be handled by a simple IF, something like this:

function h = drawEllipse(varargin)
a = varargin{1};
if isscalar(a) && ishghandle(a) && strcmpi(get(a,'type'),'axes')
    input parsing for varargin(2:end)
else
    input parsing for varargin(1:end)
    a = gca();
end