"if "function
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vijayasinthujan vijayaratnam
on 19 Feb 2012
how to write "IF" function to only accept numbers NO letters
need to ask input number (if user type any letters need to ask again to give number)
i know basic IF function but i need to know how to verified the input as number or letter ?
thank you Vijay
0 Comments
Accepted Answer
Jiro Doke
on 19 Feb 2012
You can use the isstrprop function. If answer is the input you got from your user (using the input command),
all(isstrprop(answer, 'digit'))
Here's an example:
while true
answer = input('Enter a number: ', 's');
if all(isstrprop(answer, 'digit'))
answer = str2double(answer);
break;
else
disp('Only numbers supported');
end
end
Here's another way. This way is slightly better because it allows decimal points:
while true
answer = input('Enter a number: ', 's');
answer = str2double(answer);
if ~isnan(answer)
break;
else
disp('Only numbers supported');
end
end
2 Comments
Jan
on 19 Feb 2012
The first method isstrprop(x,'digit') rejects the decimal point also, while the 2nd method accepts inputs as "3.14". In addition "1e3" should be accepted also, such that I prefer the STR2DOUBLE method.
More Answers (3)
Image Analyst
on 19 Feb 2012
Did you try using ischar() and isnumeric()? Or try something like this, or similar:
% Ask user for a number.
defaultValue = 45;
userPrompt = 'Enter the integer';
caUserInput = inputdlg(userPrompt, 'Enter the numeric value',1,{num2str(defaultValue)});
integerValue = round(str2num(cell2mat(caUserInput)));
% Check for a valid integer.
if isempty(integerValue)
% They didn't enter a number.
% They entered a character, symbols, or something else not allowed.
integerValue = defaultValue;
message = sprintf('I said it had to be an integer.\nI will use %d and continue.', integerValue);
uiwait(warndlg(message));
end
3 Comments
Image Analyst
on 19 Feb 2012
They are built in functions to check if the argument is a character or a number. Are they not in your help?
Walter Roberson
on 19 Feb 2012
In MATLAB, "if" is not a function: it is a control statement.
We've been nagging MathWorks for years to create a function equivalent to "if", but with no success yet :(
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