"For loop" not allowed in commandscript called inside nested function?

I have a basic question: I want to display 5 asterisks in the workspace (using a for loop) every time the button is pressed. I was using a command script inside my nested function. But MALTAB gave me the following error:

??? Attempt to add "k" to a static workspace. See MATLAB Programming, Restrictions on Assigning to Variables for details.

Below is my very simple code.

(1) File 1: my simpleGUI.m

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % simpleGUI.m file
    % 05/15/2012

    function simpleGui
      h.counter = 0;
      h.fig = figure('position',[1000,500,210,60]);
      h.button = uicontrol('style','pushbutton',...
          'position',[10,10,100,40],...
          'string','button');
      set(h.button,'callback',@increment);

        function increment(hObject,eventdata)   % nested function
          % command script for incrementing h.counter and displaying 5 asterisks
          increment_counter;    
          set(h.button,'string',num2str(h.counter));
        end

    end
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

(2) File 2: my command script file, increment_counter.m

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % command script file: increment_counter.m
    % 05/25/2012

    h.counter = h.counter + 1;
    for k = 1:1:5
        disp('*');
    end
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

If I comment out the for loop for asterisk display, the command script runs ok inside the nested function. But why is the for loop not allowed? Any ideas?

Thanks in advance!

Yunde

Answer 1

[Sean de Wolski]

Did you look into the link with the error message:

http://www.mathworks.com/help/releases/R2012a/techdoc/matlab_prog/f4-39683.html#f4-75258

Specifically: MATLAB issues an error if you attempt to dynamically add a variable to the workspace of an anonymous function, a nested function, or a function that contains a nested function. Examples of operations that might use dynamic assignment in this way are shown in the table below.

Assigning to a variable in a MATLAB script Convert the script to a function, where argument- and result-passing can often clarify the code as well.

[YUNDE]

Thank you Sean for looking into my question.

If I were to change the command script, increment_counter, to a function, would that be a nested function again or a regular (stand-alone) function? Could you modify my code and let me know what it should be like? The help release is really on top my head ...

Thanks again Sean!

Yunde

[Sean de Wolski]

If you were to make increment_counter a function that accepted one input (counter) and returned one (counter) and displayed the *s there would be no issue. Alternatively, you could make it a nested function (or copy its contents) and be all set too.

[YUNDE]

I tried a regular function and it worked. Thank you Sean.

Attached are my corrected code, in case it becomes helpful some day...

(1) File 1: my simpleGUI.m

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% simpleGUI.m file

% 05/15/2012

function simpleGui

h.counter = 0;

h.fig = figure('position',[1000,500,210,60]);

h.button = uicontrol('style','pushbutton',...

'position',[10,10,100,40],...

'string','button');

set(h.button,'callback',@increment);

function increment(hObject,eventdata) % nested function

% call function increment_counter

h.counter = increment_counter(h.counter);

set(h.button,'string',num2str(h.counter));

end

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

(2) File 2: my command script file, increment_counter.m

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% function file: increment_counter.m

% 05/25/2012

function output = increment_counter(input)

input = input + 1;

output = input;

for k = 1:1:5

disp('*');

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%