How to show symbolic equation answer in GUI controllers like static text

Hello,

I'm trying to create application to solve curl of functions that users input in text box and then plot however I cannot achieve to get the static text lable to show the answer. I tried (for simplicity) to assign the equation myself in the editor but it did not work, however when solving something that does not contains symbols (x, y) it works (like log(10)). In troubleshooting I tried to solve diff like that:

syms x
f = sin(5*x)
set(handles.answerTxt, 'String', diff(f));

it didn't work

however when set the answerTxt to

set(handles.answerTxt, 'String', log(10));

it works, so obviously the problem is all about how to pass symbolic equation answer in GUI components.

Thanks

Answer 1

[Walter Roberson]

set(handles.answerTxt, 'String', char(diff(f)));

[Mohamed Mounir]

Tried before but it did not work :) Thanks

[Walter Roberson]

What shows up instead ?

[Mohamed Mounir]

First, I'd like to appreciate your help and concern :) Thank you. I'm really stuck in getting this to work. All I want is to pass the results of any symbolic function like integration, differentiation, curl, divergence, .... to a static box

what you suggested returns nothing but the same error

my code as u suggested

syms f;
f=x^2;
set(handles.txtAns, 'String', char(diff(f)));

error

Undefined function or variable 'x'.

Error in test>pushbutton1_Callback (line 82)
f=x^2;

Error in gui_mainfcn (line 96)
        feval(varargin{:});

Error in test (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)test('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

[Walter Roberson]

syms x

like you had before. Not syms f

[Mohamed Mounir]

WOW !!!!!!!!!!!! Brilliant :D it works, the static text now shows 2*X thank you very very much :) thank you :) I'm speechless :D ... I will try now using the curl function and let's see what I will get

[Mohamed Mounir]

well, the curl function works great and the text shows matrix[] and the answer in between the brackets (will have to look for some tweaks in showing the results in a pretty way like a real matrix *multiplelines)

I'm trying to advance in my application and let the users input the 3 vector components that the curl will be calculated from. Input forms are xEquation, yEquation, zEquation,

syms x y z;
xInput=get(handles.xEquation, 'String');
yInput=get(handles.yEquation, 'String');
zInput=get(handles.zEquation, 'String');
set(handles.txtAns, 'String', char(curl([xInput, yInput, zInput], [x, y, z])));

For some reason it didn't work and the error says

Error using sym/curl (line 29)
Input vectors must be three-dimensional.

Error in test>pushbutton1_Callback (line 85)
set(handles.txtAns, 'String', char(curl([xInput, yInput, zInput], [x, y, z])));

Error in gui_mainfcn (line 96)
        feval(varargin{:});

Error in test (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)test('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

this error "input vector must be three-dimensional doesn't make any sense, as in the curl function I define the 3 dimensions which are variable containing the value the users input in the text box.

[Walter Roberson]

[xInput, yInput, zInput] when those are all strings, is going to result in a single concatenated string. You need to put sym() around your get()

[Mohamed Mounir]

You are a genius :) works like charm :) and many thanks for clarification why it didn't work, really helpful. I'm now working on plotting the answer of the curl :) reading about plot3 and quiver3 should help me out, right ?

Answer 2

[Azzi Abdelmalek]

Use guidata

[Mohamed Mounir]

Sounds cool however I still can't get it. Syntax says that

guidata(object_handle,data);
data = guidata(object_handle);

so now I have to write my application like this (push button callback)

syms x;
f = sin(5*x);
guidata(handles.answerTxt,data);
data = guidata(handles.answerTxt, 'String', diff(f));

I did give it a try but nothing happened. Could you please give me more clarification ?

[Azzi Abdelmalek]

To update handles

syms x;
f = sin(5*x);
handles.f=f
guidata(hObject,handles);

To get f use

f=handles.f

[Mohamed Mounir]

Dear Azzi, I'm still noob, I can't get the clue of what you're trying to say. Sorry

[Azzi Abdelmalek]

Post the function where you have problems

[Walter Roberson]

Azzi, Mohamed is trying to get a text label to contain the character representation of the differentiation of the symbolic expression "f", not trying to store the symbolic expression itself.

[Mohamed Mounir]

I did try everything with guidata, and I did read about it in the help but nothing helped me through what I'm trying to achieve