while loop with OR statement

I am trying to ask a user input a real, positive number by using input function and checking the condition with a while loop. I am successful to check is the number is real and positive but I could not figure out how to correct if the user inputs a character.

K=input('Enter the K value = ', 's');
% I ask as string because if the user enters a character I want to give warning   
%rather than code is not working.

K=str2num(K); % convert string to a number
sK=size(K);   % if K is a character its size will be  0 0
sK=sK(1);
while (isnan(K)) || (any(imag(K)))|| ((K<=0)) 
     disp('Number of domains input needs to be real and positive')
     K=input('Enter the K value = ', 's');
     K=str2num(K);
     sK=size(K);
     sK=sK(1);
 end

% This while loop works but I can not check for if the input was a character 
while (isnan(K)) || (any(imag(K)))|| ((K<=0))  || (sK==0)    % get an error Operands to the || and && operators must be 
%convertible to logical scalar values.

Any thoughts where I make a mistake?

(in the second while I can't write in the question , I dont know why. But I know there should be between statements) Thank you

[Kamuran]

Or simpler problem I am having. I decided to separate the while loop into two while loops. In the first one I am checking if the user enter a alphabetic character first.

% Asking user to input the variable Out1=input(['Enter the beginning point of the domain = '],'s'); Out2=input(['Enter the ending point of the domain = '],'s');

Out1=str2num(Out1); sK1=size(Out1); % if OUT1 is not a number, sK1 will be 0 by 0 sK1=sK1(1); Out2=str2num(Out2); sK2=size(Out2); % if OUT2 is not a number, sK2 will be 0 by 0 sK2=sK2(1); while (sK1==0) (sK2==0)

    Out1=input(['Enter the starting point of the domain = '],'s'); 
    Out2=input(['Enter the ending point of the domain = '],'s'); 
    Out1=str2num(Out1);
    sK1=size(Out1);
sK1=sK1(1);
    Out2=str2num(Out2);
    sK2=size(Out2);
sK2=sK2(1);
    end

This does not work ..but if I check 1 by 1 it does work ..I dont understand why.

Any suggestion?

Answer 1

[Image Analyst]

Here is the snippet I use:

% 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

It should be easy to modify to handle just one input instead of 2.

[Kamuran]

Thank you. I will be able to modify it from your idea.