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Input is a valid integer

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Pavithra Naidu
Pavithra Naidu 2015-10-29
编辑： DGM 2024-5-31
How to check if the value entered by the user is a valid integer and not a negative number(such as -1,-9,-10 etc) or characters/strings(such as a, i,thank you)or special symbols(such as @,* etc) and also that is not equal to 0?

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回答（2 个）

Walter Roberson
Walter Roberson 2015-10-29
https://www.mathworks.com/matlabcentral/newsreader/view_thread/163080
DGM
DGM 2024-5-31
编辑：DGM 2024-5-31
Ran in:
Assuming the input x is a char vector from input() which represents a numeric scalar:
isvalidnumber('56') % positive scalar integer is okay
ans = logical
1
isvalidnumber('-56') % not valid (not positive)
ans = logical
0
isvalidnumber('56.2') % not valid (noninteger)
ans = logical
0
isvalidnumber('[56 23]') % not valid (nonscalar)
ans = logical
0
isvalidnumber('asdf') % not valid (non-numeric)
ans = logical
0
isvalidnumber('56E3') % E-notation is valid (56000 is a positive scalar integer)
ans = logical
1
function isvalid = isvalidnumber(x)
x = str2double(x); % NaN if text or nonscalar numeric
isvalid = (x > 0) & (mod(x,1) == 0); % true only for positive integers
end
There are probably other ways to approach this, but it's a basic start. If you really want to improve things, take a step back and stop designing around accumulating parameters interactively via input().

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