"if "function

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

Answer 1

[Jiro Doke]

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

[vijayasinthujan vijayaratnam]

100% it is working

[Jan]

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.

Answer 2

[Wayne King]

Hi Vijay

if isletter(input)
disp('Please enter a number, not a letter');
end

[vijayasinthujan vijayaratnam]

hi Wayne king

i knew that but if the user type mistake, then he/she need to re-start the program(need to input more detail from begin, this can make him bored )

Answer 3

[Image Analyst]

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

[vijayasinthujan vijayaratnam]

i dont know what is ischar and isnumeric

can you explain me please

[Image Analyst]

They are built in functions to check if the argument is a character or a number. Are they not in your help?

[Jan]

Simply use "help ischar" and "help isnumeric".

Answer 4

[Walter Roberson]

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 :(

[vijayasinthujan vijayaratnam]

ok