the capacitor_value is returning Nan

Question

Badr Al-Sabri 2022-5-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1713820-the-capacitor_value-is-returning-nan

评论： Voss 2022-5-7

采纳的回答： Voss

% --- Executes on button press in calculate_button.

function calculate_button_Callback(hObject, eventdata, handles)

option = get(handles.resistance_value, 'value');

switch option

case 1

R = 1000;

case 2

R = 2000;

case 3

R = 3000;

case 4

R = 4000;

end

R = str2double(R);

f_c = get(handles.f_value,'string');

f_c = str2double(f_c);

c_value = 1 / (2*pi*R*f_c);

c_value = num2str(c_value);

set(handles.capacitor_value,'string',c_value);

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Answer 1

Voss 2022-5-7

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1713820-the-capacitor_value-is-returning-nan#answer_959220

在 MATLAB Online 中打开

In the switch block, R is set to a double already, so it is not correct to do str2double after that. In fact, doing so makes R into NaN:

% option = get(handles.resistance_value, 'value');
option = 1; % hard-coded for demonstration
switch option
    case 1
        R = 1000;
    case 2
        R = 2000;
    case 3
        R = 3000;
    case 4
        R = 4000;
end        
R = str2double(R)
R = NaN

So then C calculated from R=NaN is NaN as well:

% f_c = get(handles.f_value,'string');
f_c = '33'; % hard-coded for demonstration
f_c = str2double(f_c);
c_value = 1 / (2*pi*R*f_c)
c_value = NaN
c_value = num2str(c_value)
c_value = 'NaN'

Simply remove the erroneous R = str2double(R); line:

% option = get(handles.resistance_value, 'value');
option = 1; % hard-coded for demonstration
switch option
    case 1
        R = 1000;
    case 2
        R = 2000;
    case 3
        R = 3000;
    case 4
        R = 4000;
end        
% R = str2double(R);
% f_c = get(handles.f_value,'string');
f_c = '33'; % hard-coded for demonstration
f_c = str2double(f_c);
c_value = 1 / (2*pi*R*f_c)
c_value = 4.8229e-06
c_value = num2str(c_value)
c_value = '4.8229e-06'