gui popupmenu problem with limits

Question

Alicja 2023-1-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1895795-gui-popupmenu-problem-with-limits

回答： Raghav 2023-4-5

Hello, I want to create an app that counts the limit of a function at an exact point. I need to use a popup menu to select whether the border is to the right or left. There's my code, why isn't it working? Could you help me?

function mat
f = figure('Visible','off',...
    'Position',[480,500,500,480]);
pushbutton = uicontrol('Style','pushbutton',...
    'String','count',...
    'Position',[285,63,70,25],...
    'Callback',@border);
hinput_g = uicontrol('Style','edit',...
    'Position',[120, 200,240,35],...
    'String','function','FontSize',13, 'FontName','silom');
hinput_granica  = uicontrol('Style','edit',...
    'Position',[120, 100,240,35],...
    'String','limit at point','FontSize',13);
hpopup_g = uicontrol('Style','popup',...
    'String',{'right','left'},...
    'Position',[130,50,140,35]);
set(f,'Name','My app gui');
set(f,'Visible','on');
function border(~,~)
x = get(hinput_g,'String');
x = str2sym(x);
a = get(hinput_granica, 'String')
a = str2num(a);
idx = get(hpopup_g,'Value'); 
str = get(hpopup_g, 'String');
popup_str = str{idx};
if popup_str == 'right'
    c = limit(x, a,'right');
    msgbox(sprintf(char(c)));
    
elseif popup_str == 'left'
    c = limit(x, a,'left');
    msgbox(sprintf(char(c)));
end
end
end

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Alicja 2023-1-17

nothing has changed :/

Torsten 2023-1-17

编辑：Torsten 2023-1-17

You are missing an argument in the call to limit (see above).

And make sure that the first two arguments are of symbolic type (what you can check by the call to "class").

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Answer 1

Raghav 2023-4-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1895795-gui-popupmenu-problem-with-limits#answer_1209464

Hi,

Based on your question, I understand that you are facing difficulty using limit function.

The error message suggests that the variable a is not a symbolic variable.

In the border function, you are converting the string input from the hinput_granica edit box to a numeric value using the str2num function. However, limit function from the Symbolic Math Toolbox expects a symbolic variable as the second input, not a numeric value.

To fix the issue, you should create a symbolic variable using the sym function and use it as the second input to the limit function.

The official documentation for limit & sym function is mentioned below respectively:

https://www.mathworks.com/help/symbolic/sym.limit.html

https://www.mathworks.com/help/symbolic/sym.html

Hope it helps!

Thanks,

Raghav Bansal