为MATLAB plot函数实现多种语法 [英] Implementing multiple syntaxes for a MATLAB plot function

问题描述

MATLAB和工具箱中的许多绘图功能(并非全部)都支持以下两种语法:

Many of the plotting functions in MATLAB and toolboxes (thought not all) allow both the following syntaxes:

plotfcn(data1, data2, ...)
plotfcn(axes_handle, data1, data2, ...)

第一个绘制到当前轴(gca)中，或者创建并绘制到新轴(如果不存在).第二个以手柄axes_handle绘制到轴中.

The first plots into the current axes (gca) or creates and plots into a new axes if none exists. The second plots into the axes with handle axes_handle.

研究了几个MATLAB和工具箱绘图函数的内部结构，看来MathWorks并没有真正标准化的方法.一些绘图例程使用内部但开放的函数axescheck来解析输入参数.有些人对第一个输入参数进行简单检查；有些使用更复杂的输入解析子功能，可以处理更多种输入语法.

Having looked into the internals of several MATLAB and toolbox plotting functions, it looks like there isn't really a standardised way that MathWorks do this. Some plotting routines use the internal, but open, function axescheck to parse the input arguments; some do a simple check on the first input argument; and some use a more complex input-parsing subfunction that can handle a larger variety of input syntaxes.

请注意，axescheck似乎使用了未记录的语法ishghandle-文档说ishghandle仅接受一个输入，如果它是任何Handle Graphics对象，则返回true；否则，返回true.但是axescheck将其称为ishghandle(h, 'axes')，仅当它是轴对象时才返回true.

Note that axescheck appears to use an undocumented syntax of ishghandle - the doc says that ishghandle takes only one input, returning true if it is any Handle Graphics object; but axescheck calls it as ishghandle(h, 'axes'), which returns true only if it's specifically an axes object.

有人知道实现此语法的最佳实践或标准吗?如果没有，您发现哪种方法最可靠?

Is anyone aware of a best practice or standard for implementing this syntax? If not, which way have you found to be most robust?

推荐答案

如果仍然有人感兴趣，在我发布问题四年后，这就是我主要解决的模式.

In case anyone is still interested, four years after I posted the question, this is the pattern that I have mostly settled on.

function varargout = myplotfcn(varargin)
% MYPLOTFCN Example plotting function.
%
% MYPLOTFCN(...) creates an example plot.
%
% MYPLOTFCN(AXES_HANDLE, ...) plots into the axes object with handle
% AXES_HANDLE instead of the current axes object (gca).
%
% H = MYPLOTFCN(...) returns the handle of the axes of the plot.

% Check the number of output arguments.
nargoutchk(0,1);

% Parse possible axes input.
[cax, args, ~] = axescheck(varargin{:});

% Get handle to either the requested or a new axis.
if isempty(cax)
    hax = gca;
else
    hax = cax;
end

% At this point, |hax| refers either to a supplied axes handle,
% or to |gca| if none was supplied; and |args| is a cell array of the
% remaining inputs, just like a normal |varargin| input.

% Set hold to on, retaining the previous hold state to reinstate later.
prevHoldState = ishold(hax);
hold(hax, 'on')          


% Do the actual plotting here, plotting into |hax| using |args|.


% Set the hold state of the axis to its previous state.
switch prevHoldState
    case 0
        hold(hax,'off')
    case 1
        hold(hax,'on')
end

% Output a handle to the axes if requested.
if nargout == 1
    varargout{1} = hax;
end  

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