MATLAB: “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

Best Answer

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

Related Solutions

MATLAB: Help me with Input from keyboard

Here are my number input snippets. Feel free to modify/adapt:

% Ask user for one integer number.
defaultValue = 45;
titleBar = 'Enter a value';
userPrompt = 'Enter the integer';
caUserInput = inputdlg(userPrompt, titleBar, 1, {num2str(defaultValue)});
if isempty(caUserInput),return,end; % Bail out if they clicked Cancel.

% Round to nearest integer in case they entered a floating point number.
integerValue = round(str2double(cell2mat(caUserInput)));
% Check for a valid integer.
if isnan(integerValue)
    % They didn't enter a number.  

    % They clicked Cancel, or 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
% Ask user for two floating point numbers.
defaultValue = {'45.67', '78.91'};
titleBar = 'Enter a value';
userPrompt = {'Enter floating point number 1 : ', 'Enter floating point number 2: '};
caUserInput = inputdlg(userPrompt, titleBar, 1, defaultValue);
if isempty(caUserInput),return,end; % Bail out if they clicked Cancel.
% Convert to floating point from string.
usersValue1 = str2double(caUserInput{1})
usersValue2 = str2double(caUserInput{2})
% Check for a valid number.
if isnan(usersValue1)
    % They didn't enter a number.  
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
  % Convert the default from a string and stick that into usersValue1.
    usersValue1 = str2double(defaultValue{1});
    message = sprintf('I said it had to be a number.\nI will use %.2f and continue.', usersValue1);
    uiwait(warndlg(message));
end

MATLAB: How to Enter Threshold Value Depend on the Selected Image

Try this to ask your user for an integer value for the threshold:

% Ask user for one integer number.
defaultValue = 45;
titleBar = 'Enter an integer value';
userPrompt = 'Enter the threshold';
caUserInput = inputdlg(userPrompt, titleBar, 1, {num2str(defaultValue)});
if isempty(caUserInput),return,end; % Bail out if they clicked Cancel.
% Round to nearest integer in case they entered a floating point number.
integerValue = round(str2double(cell2mat(caUserInput)));
% Check for a valid integer.
if isnan(integerValue)
    % They didn't enter a number.  
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    integerValue = defaultValue;
    message = sprintf('I said it had to be an integer.\nTry replacing the user.\nI will use %d and continue.', integerValue);
    uiwait(warndlg(message));
end

Best Answer

Related Solutions

MATLAB: Help me with Input from keyboard

MATLAB: How to Enter Threshold Value Depend on the Selected Image

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