在MATLAB中衍生gui？ [英] Derivative in MATLAB gui?

问题描述

我试图计算一个编辑文本框（edit1）的派生值，并在静态文本框（text1）中显示答案。但它只是显示数字。我做错了什么？

 ％---在按钮按钮1上执行按钮。 
函数pushbutton1_Callback（hObject，eventdata，句柄）
％pushbutton1的对象句柄（见GCBO）
％eventdata保留 - 在将来版本的MATLAB中定义
句柄结构带有句柄和用户数据（参见GUIDATA）
x = -10：.1：10; 
 equation = get（handles.edit1，'String'）; 
 y = eval（equation）; 
 derive_func = diff（y）; 
 set（handles.text1，'String'，derive_func）; 
 plot（y）; 
  

GUI Image -
正如您所看到的，它绘制了该函数，但在尝试区分时会返回3行数字：

diff 的两种不同用法之间存在冲突。默认的内置使用是数字区分，并且您正在将该函数应用于数字变量 y ，以便获得数字输出。

您似乎想要做的是使用符号数学工具箱中的 diff 来显示 5 * x ^ 4 ，这就要求你告诉matlab你要使用符号数学工具箱，通过提供正确的输入diff，通常是一个字符串。

我正在使用matlab R14，并且在新版本的sym工具箱中进行了很多更改，但以下内容适用于您。

  str ='x ^ 5'; 
 diff（str，'x'）
  

其中 str 是您想要象征性地区分的表达式。请注意，在我的版本中，sym工具箱对符号 x。^ 5 并且倾向于 x ^ 5 ，I不知道它如何在MuPad上工作，但您可能必须找到一种解决方法，以确保您使用它可以处理的字符串来馈送MuPad（或您正在使用的任何一种sym引擎）。

编辑

有关使用 cd 或 addpath 来控制使用哪个版本的重载函数 diff 已被删除。

I'm trying to calculate the derivative of a an edit text box (edit1) and display the answer in a static text box (text1). But it is just displaying numbers. What am I doing wrong?

% --- 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)
x=-10:.1:10;
equation = get(handles.edit1, 'String');
y = eval(equation);
derive_func = diff(y);
set(handles.text1, 'String', derive_func);
plot(y);

GUI Image - As you can see, it plots the function, but returns with 3 lines of numbers when it tries to differentiate:

解决方案

You are seeing a conflict between two different uses of the overloaded function diff. The default builtin use is numeric differentiation, and you are applying the function to numeric variable y so you are getting numeric output.

What you seem to want to do is use diff from the symbolic math toolbox to diplay 5*x^4 and that requires that you tell matlab that you want to use the symbolic math toolbox by providing diff with the right input, usually a string.

I am using matlab R14 and a lot has changed in the sym toolbox with newer versions, but the following should work for you.

str = 'x^5';
diff(str,'x')

where str is the expression you want to differentiate symbolically. Note that in my version the sym toolbox is unhappy with the notation x.^5 and prefers x^5, I don't know how it might work on MuPad, but you may have to find a workaround to make sure that you feed MuPad (or whichever sym engine you are using) with a string it can handle.

edit

Earlier suggestions on the use of cd or addpath to control which version of overloaded function diff is used have been removed.

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