integration of equation using gui

Question

Alicja 2023-1-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1895620-integration-of-equation-using-gui

评论： John D'Errico 2023-1-17

Hello, I want to find integration of equation using gui. That's my code, why it doesn't work? Please help me and explain in very simple words, I'm at the very beginning of learning matlab.

function calculator

% tworzenie okna GUI

f = figure('Visible','off',...

'Position',[480,500,500,480]);

integration = uicontrol('Style','pushbutton',...

'String','integration',...

'Position',[315,170,70,25],...

'Callback',@integration);

hinput_g = uicontrol('Style','edit',...

'Position',[120, 200,240,40],...

'String','function');

set(f,'Name','Moja aplikacja GUI');

set(f,'Visible','on');

function integration(~,~)

x = get(hinput_g,'String');

x=str2func(x);

syms c

c= int(x)

msgbox(sprintf(c));

end

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Alicja 2023-1-17

yes, autocorrect, thanks

John D'Errico 2023-1-17

Blasted spell checkers. I'll never forgive the old IBM utility, which many years ago, could find only one replacement for what it thought was my mis-spelled name of D'Errico in a document. It wanted to substitute "derelict" for my name.

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Answer 1

John D'Errico 2023-1-17

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1895620-integration-of-equation-using-gui#answer_1150565

编辑：John D'Errico 2023-1-17

在 MATLAB Online 中打开

I can't execute this code in online MATLAB. So we can just look at what happens inside the function caled integration.

First, it extracts a variable named x, as a string from the gui field. Perhaps it was this:

x = 'y^2 + 2';

Next, you use str2func. That is incorrect. You don't want to make it a function handle like this:

x=str2func(x)

That is because int does not use function handles. Instead, what you wanted to do was to use str2sym.

x = str2sym(x)

x =

This is something that int can now use. As you can see, MATLAB now thinks x is a symbolic expression.

Next, you create a symbolic variable named c. There is no need to do so, since immediately afterwards, you assign the result of int to c. That overwrites anything you did before. So the "syms c" command is wasted. Not important though, except for the CPU cycles thrown in the bit bucket. One day you will care about wasted CPU cycles.

Finally, you use int. That will work now.

c= int(x)

c =

However, can you use sprintf directly on c? No. However, you can convert c into a character form.