matlab代码实现：Matlab 绘图界面设计：（1）设计 GUI 界面；（2）通过下拉菜单选择绘制正弦、正切信号；（3）通过编辑框输入命令，根据命令绘制信号；（4）通过按钮在图形中输出标注（标题、各轴名称）。

以下是一个基于 GUIDE 工具箱实现的 Matlab 代码，可以实现绘制正弦、正切信号并输出标注：

1. 打开 Matlab 并创建一个新的 GUI 界面。
2. 在 GUIDE 工具箱中，添加一个下拉菜单、一个编辑框和一个按钮控件，并设置它们的位置和大小。
3. 给下拉菜单添加两个选项：“Sine”和“Tangent”。
4. 在编辑框中输入命令，例如"sin(x)"或"tan(x)"。
5. 在按钮的 Callback 函数中编写绘图代码，通过下拉菜单和编辑框中的命令绘制信号，并在图形中输出标注（标题、各轴名称）。

以下是完整的 Matlab 代码：

function varargout = plot_tool(varargin)
% PLOT_TOOL MATLAB code for plot_tool.fig
%      PLOT_TOOL, by itself, creates a new PLOT_TOOL or raises the existing
%      singleton*.
%
%      H = PLOT_TOOL returns the handle to a new PLOT_TOOL or the handle to
%      the existing singleton*.
%
%      PLOT_TOOL('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in PLOT_TOOL.M with the given input arguments.
%
%      PLOT_TOOL('Property','Value',...) creates a new PLOT_TOOL or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before plot_tool_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to plot_tool_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help plot_tool

% Last Modified by GUIDE v2.5 19-Apr-2021 22:50:27

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @plot_tool_OpeningFcn, ...
                   'gui_OutputFcn',  @plot_tool_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT


% --- Executes just before plot_tool is made visible.
function plot_tool_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to plot_tool (see VARARGIN)

% Choose default command line output for plot_tool
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes plot_tool wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = plot_tool_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;


% --- Executes on selection change in popupmenu1.
function popupmenu1_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: contents = cellstr(get(hObject,'String')) returns popupmenu1 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupmenu1


% --- Executes during object creation, after setting all properties.
function popupmenu1_CreateFcn(hObject, eventdata, handles)
% hObject    handle to popupmenu1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: popupmenu controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get selected option from popupmenu
popup_val = get(handles.popupmenu1, 'Value');

% Get command from editbox
command = get(handles.edit1, 'String');

% Generate x and y values
if popup_val == 1 % Sine
    x = linspace(0, 2*pi, 100);
    y = eval(command);
elseif popup_val == 2 % Tangent
    x = linspace(-pi/2, pi/2, 100);
    y = eval(command);
end

% Plot data
plot(handles.axes1, x, y);

% Add labels
title(handles.axes1, 'Plot Tool');
xlabel(handles.axes1, 'X Axis');
ylabel(handles.axes1, 'Y Axis');


% --- Executes during object creation, after setting all properties.
function edit1_CreateFcn(hObject, eventdata, handles)
% hObject    handle to edit1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

在 GUIDE 工具箱中完成以上步骤后，点击“Generate M-File”生成 Matlab 代码，即可得到上述代码。运行该代码，就可以使用绘图工具了。