How can i add a error check to this program such that the input must only be in numbers?

Question

Rishith Bommireddipalli 2018-4-15

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/395010-how-can-i-add-a-error-check-to-this-program-such-that-the-input-must-only-be-in-numbers

评论： Rishith Bommireddipalli 2018-4-15

I want to add error checks to this program such that the 'value' input must only be in numbers and the program must keep asking the user for input until the user enters valid number instead of letters or symbols for 'value'.

x=input('choose between 1 to 3') 
  value = input('Enter any value that you want to convert:','s');
   switch x
    case 1
    result= value+20
    case 2
    result=value+30
    case 3
    result=value+70
    otherwise
    end

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Answer 1

Birdman 2018-4-15

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/395010-how-can-i-add-a-error-check-to-this-program-such-that-the-input-must-only-be-in-numbers#answer_315200

编辑：Birdman 2018-4-15

在 MATLAB Online 中打开

Try this:

x=input('choose between 1 to 3') 
while true
value = input('Enter any value that you want to convert:','s');
if ~isnan(str2double(value))
    value=str2double(value);
    break;
else
    errordlg('Wrong type of value entered. Try again.');
end
end
   switch x
    case 1
    result= value+20
    case 2
    result=value+30
    case 3
    result=value+70
    otherwise
    end

The key code is

~isnan(str2double(value))

This converts the value variable to double and isnan function checks whether the conversion resulted in NaN or numeric variable. According to that, the while loop is broken.