how to create an error message when invalid data is input and then prompt to re-enter the data

person_age = input('Please enter persons age')
If person_age < 1 
        errordlg('Please input valid number','Error')
end

How do I display this error message and then prompt the user to re-enter the person_age?

Many thanks

Answer 1

[JESUS DAVID ARIZA ROYETH]

person_age = input('Please enter persons age');
while person_age < 1 
        errordlg('Please input valid number','Error')
        person_age = input('Please enter persons age');
end

[Eddie Burns]

Many thanks that worked, what if I also needed another error message for the same input

person_age > 120

Would I need to do another seperate while sequence?

[JESUS DAVID ARIZA ROYETH]

person_age = input('Please enter persons age');
errors={'Please input valid number >1','Please input valid number <=120'};
while person_age < 1 || person_age>120
        errordlg(errors([person_age < 1 person_age>120]) ,'Error')
        person_age = input('Please enter persons age');
end

[Eddie Burns]

thank you worked perfectly. Another question how would i say 'only accept the ages 10, 20 or 30' any other number input is invalid, show error message like above

[JESUS DAVID ARIZA ROYETH]

person_age = input('Please enter persons age');
errors={'Please input valid number >1','Please input valid number <=120'};
while person_age < 1 || person_age>120
        errordlg(errors([person_age < 1 person_age>120]) ,'Error')
        person_age = input('Please enter persons age');
end
values=[10 20 30];
if ~ismember(person_age,values)
    error(['only accept the ages ' num2str(values,'%i ')])
end

Answer 2

[Guillaume]

Typical pattern for this is:

value = someinvalidvalue;
while valueisinvalid
    value = input('Enter value');    
end

Note that your test is extremely incomplete. Any of the following inputs would be considered valid age:

• NaN
• [-1, 2]
• Inf
• 'abcdef'
• 5 + 1i*2

You may want to change your test to:

while isnumeric(person_age) || isscalar(person_age) || isreal(person_age) || isfinite(person_age) || person_age < 1

[Eddie Burns]

Many thanks for response, it is a simple machine learning database I am being assesed on, I dont think it requires that level of detail.