Adding Polynomials Using App Designer

I am new to matlab and I am trying to create a calculator that adds polynomials. I want the user to input something like 3*x+1 and 4*x+1 and have a result of 7*x+2. here is my code but when I try it, it does not display any answer:

        % Button pushed function: AddButton
        function AddButtonPushed(app, event)
          a = str2num(app.fxEditField.Value);
          b = str2num(app.gxEditField.Value);
          res = a+b;
          app.ResultEditField.Value = num2str(res);
        end

Answer 1

[Kevin Holly]

How did you want your user to input the data? As for the calculations, see below for an example.

app.fxEditField.Value = [3 1];
app.gxEditField.Value = [4 1];

AddButtonPushed(app)

a = 

b = 

res = 

app = struct with fields:
        fxEditField: [1×1 struct]
        gxEditField: [1×1 struct]
    ResultEditField: [1×1 struct]

function AddButtonPushed(app, event)
    a = poly2sym(app.fxEditField.Value)
    b = poly2sym(app.gxEditField.Value)
    res = a+b
    app.ResultEditField.Value =res
end

[jinji gneiss]

Good day! I want the user to input the data in symbolic form (e.g. 3*x+2). I think that matlab just recognizes the inputed symbolic form as plain text and I am trying to find a way in which matlab will recognize the input as a symbolic function. I am new to matlab and I am really not sure if what I want to happen is possible. Any advice would be much appreciated.

[Kevin Holly]

Please see app attached.

app.fxEditField.Value = '3*x+1';
app.gxEditField.Value = '4*x+1';

AddButtonPushed(app);

res = 

ResultEditField_Value = '7*x + 2'

Below is the callback for the "Add" button.

function AddButtonPushed(app, event)            
    a = str2sym(app.fxEditField.Value);
    b = str2sym(app.gxEditField.Value);
    
    res = a+b;
    app.ResultEditField.Value = char(res);
end

[jinji gneiss]

This is exactly what I am looking for! Thank you very much I got it working already. My mistake was I didn't consider char(res).