MATLAB: How to get functions out of inputdlg

inputdlg

questions = {'Enter a function','Enter a lower limit','Enter an upper limit'};

prompt = inputdlg(questions)
equation = str2num(prompt{1})
lower_limit = str2num(prompt{2})
upper_limit = str2num(prompt{3})
P=int(sym('equation'),lower_limit,upper_limit)

Hello everyone. My question is how do I keep the inputted equation (such as x.^2) as itself, instead of it changing to x. When I run the program below (you should be able to copy and paste it if you want to run it) the inputted function gets changed to x. Many thanks.

Best Answer

I would do something like this, using str2func and vectorize:

questions = {'Enter a function of ‘x’','Enter a lower limit','Enter an upper limit'};
prompt = inputdlg(questions)
equation = str2func(['@(x) ',vectorize(prompt{1})])
lower_limit = str2num(prompt{2})
upper_limit = str2num(prompt{3})
P=integral(equation,lower_limit,upper_limit)

Experiment to get different results.

Related Solutions

MATLAB: How to limit the range of numbers that can be entered into a MATLAB GUI text box

To constrain the input to a MATLAB GUI text box, you must develop code to check the input and update the text box accordingly.

To limit the range of input to a number between 1 and 100, you can incorporate the following code in the callback function of the text box. Please note that the code can be used with text boxes that contain strings or cell arrays.

x = get(hObject,'String');  % get text from handles structure
try
      y = x{1};               % cell to string
      z = str2num(strtok(y));         % string to number

catch
      z = str2num(strtok(x));          % string to number
end
lower_limit = 1;
upper_limit = 100;
%Output equals value of z if z falls between the bounds set by lower_limit
%and upper_limit. Otherwise it is 0 or an empty array
output = z*(z < upper_limit)*(z > lower_limit);
%If z does not fall within the bounds set by the limit parameters or is an
%empty array
if isempty(output) | (~output)
      %Set the output value to the limit value closest to z
      output = lower_limit*(z < lower_limit) + upper_limit*(z > upper_limit);
      %If there is no value in z, set the output value to the lower limit of
      %the desired bounds
      if isempty(output)
          output = lower_limit;
      end
      %Create a message string and initiate a message box informing the user
      %to enter a value within the limits of the defined range
      str = sprintf('Enter a number between %d and %d', lower_limit, upper_limit);
      msgbox(str);
end
%Set the value of the text box to the new value, which lies within the
%value range
set(hObject,'String',{num2str(output(1))});

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

Best Answer

Related Solutions

MATLAB: How to limit the range of numbers that can be entered into a MATLAB GUI text box

MATLAB: Help me with Input from keyboard

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