Not getting Error message

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Avinav Kumar
Avinav Kumar 2021-9-23
回答： Walter Roberson 2021-9-23
I am trying to get an error message if my a value is left empty by user. But i am not getting the same. If someone can help.My code is as follows.
function Run_Callback(hObject, eventdata, handles)
% hObject handle to Run (see GCBO)
% eventdata reserved - to be defined in edit1 future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
a=str2double(get(handles.edit1,'string'));
b=str2double(get(handles.edit2,'string'));
c=str2double(get(handles.edit3,'string'));
d=str2double(get(handles.edit4,'string'));
e=str2double(get(handles.edit5,'string'));
f=str2double(get(handles.edit6,'string'));
g=str2double(get(handles.edit7,'string'));
h = a *((b/c)*(d/e)^2*(f/g))^(1/5);
if isempty(a)
errordlg('Please enter value ofDreference','Error Code I');
else
set(handles.edit8,'string',num2str(h));
end

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回答（1 个）

Walter Roberson
Walter Roberson 2021-9-23
Ran in:
AnEmptyString = '';
str2double(AnEmptyString)
ans = NaN
When you str2double() something empty, you get NaN, not empty. You need to check the result of the get() if you want to distinguish between the user entering nothing, or the user entering 'NaN', or the user entering something that is not number-like.

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