NaN error when trying to display calculation result

Hi,

When I try to run this code, the static text always says NaN?

I enter numbers for a, b and c. Then i try to do some calculations with these values and then try to display the answer "discriminant_string" in the static text box called Result_Text.

Why does it give me this result?

I'm using Matlab GUIDE for the GUI

Here is the code

a = get(handles.A_Value,'String');

b = get(handles.B_Value,'String');

c = get(handles.C_Value,'String');

p1 = str2double(b) * str2double(b);

p2 = str2double(a) * str2double(c) * 4;

discriminant = str2double(p1) * str2double(p2);

discriminant_string = num2str(discriminant);

set(handles.Result_Text,'String',discriminant_string);

Thank you very much, im just starting out :)

[Oliver Ferenczi]

Im using the Matlab Guide for the GUI

Answer 1

[JESUS DAVID ARIZA ROYETH]

solution:

  a = get(handles.A_Value,'String');
    b = get(handles.B_Value,'String');
    c = get(handles.C_Value,'String');
    p1 = str2double(b) * str2double(b); 
    p2 = str2double(a) * str2double(c) * 4;
    discriminant = p1 * p2;
    discriminant_string = num2str(discriminant);
    set(handles.Result_Text,'String',discriminant_string);