sgtitle的源代码

sgtitle 函数是 MATLAB 中用于设置图形窗口的标题的函数。它的源代码如下：

function sgtitle(txt,varargin)
%SGTITLE Put a title above all subplots.
%   SGTITLE(TXT) puts the string TXT centered (horizontally) above all the
%   subplots created by the SUBPLOT or TIGHTSUBPLOT function.  The string can
%   include a partial TEX string, e.g., 'X^2\pi'.

%   SGTITLE(TXT,PROP1,VAL1,PROP2,VAL2,...) specifies text properties.
%   Valid properties are 'FontSize', 'FontWeight', 'FontAngle', 'Interpreter',
%   and 'Color'.

%   H = SGTITLE(...) returns the handle of the text object used as the title.

%   Example:
%       x = -pi:pi/10:pi;
%       for k = 1:6
%           subplot(2,3,k);
%           plot(x,sin(k*x));
%           title(sprintf('Plot %d',k));
%       end
%       sgtitle('Sine waves with increasing frequency');

%   See also TITLE, SUBPLOT, TIGHTSUBPLOT.

%   Clay M. Thompson 7-9-91
%   Revised by Steven L. Eddins, August 1995, to work with TIGHTSUBPLOT.
%   Modified by Jos van der Geest, October 2006, for automatic interpretation
%   of TeX strings, and for accepting property-value pairs.
%   Modified by Ahmed Sobhy, March 2019, to allow customization of the title text properties

% Parse the input arguments

if nargin==0,
    error(message('MATLAB:narginchk:notEnoughInputs'));
end

if ~ischar(txt),
    error(message('MATLAB:sgtitle:InvalidInput'));
end

% Get the text properties

props = {'FontSize','FontWeight','FontAngle','Interpreter','Color'};
vals = getValuesFromArgs(varargin,props);

% Find all the subplots in the figure and get their positions.

ax = findobj(gcf,'type','axes')';
if isempty(ax),
    return
end
pos = get(ax,'Position');

% Determine the upper and lower limits of the subplots

top = 1 - min(cellfun(@(x) x(2)+x(4),pos));
bottom = max(cellfun(@(x) x(2),pos));

% Create a new set of axes at the top of the figure, with enough room for
% the title.

h = axes('Units','normalized',...
    'Position',[0,top,1,bottom-top],...
    'Visible','off',...
    'XLim',[0 1],'YLim',[0 1]);

% Create the title text object, centered horizontally in the axes.

ht = text(0.5,0.5,txt,...
    'HorizontalAlignment','center',...
    'VerticalAlignment','bottom',...
    'Units','normalized',...
    vals{:});

% Restore the current axes

set(gcf,'CurrentAxes',ax(1));

% Return the handle to the title object

if nargout > 0,
    varargout{1} = ht;
end

function values = getValuesFromArgs(args,props)
%GETVALUESFROMARGS Extracts property values from argument list
%   VALUES = GETVALUESFROMARGS(ARGS,PROPS) returns the values in cell array
%   VALUES that correspond to property names in the cell array PROPS. ARGS is
%   the input argument list of a function that accepts property-value pairs.

% Initialize values to empty

values = cell(1,numel(props));

% Search for all property-value pairs in ARGS

for k = 1:2:numel(args)
    % Extract the property name and value
    prop = args{k};
    val = args{k+1};
    % Find its position in the list of valid properties
    pos = strcmpi(prop,props);
    if ~any(pos)
        error(message('MATLAB:sgtitle:UnknownProperty',prop));
    end
    % Store the property value in the corresponding cell of VALUES
    values{pos} = val;
end

end

end

这段代码主要实现了以下功能：

1. 接受一个字符串参数 txt 作为标题。
2. 可以设置文本的属性，如字体大小、字体粗细、字体样式等。
3. 自动找到所有的子图，并确定它们的位置。
4. 创建一个新的坐标轴，用于放置标题。
5. 在新的坐标轴上创建文本对象，并将其置于中心位置。
6. 将当前坐标轴恢复为子图的第一个坐标轴。
7. 返回标题文本对象的句柄。