outputs in my function

Hello,Im need to use the output "a" in other function who calls testkeyboard, but when i do it, occurs the next error:

Output argument "rueda1" (and maybe others) not assigned during call to

this is the code of testkeyboard:

function [rueda1,rueda2,rueda3]=testkeyboard
  figure('KeyPressFcn',@printfig);

    function [rueda1,rueda2,rueda3] =printfig(~,event)
    % Callback to parse keypress event data to print a figure
        if event.Character == 'w'
           rueda2=0;
           rueda1=1;
           rueda3=0;
        elseif event.Character == 's'
           rueda2=0;
           rueda1=-1;
           rueda3=0;
        elseif event.Character == 'a'          
           rueda2=-1;
           rueda1=0;
           rueda3=0;
        elseif event.Character == 'd'
           rueda2=1;
           rueda1=0;
           rueda3=0;
        elseif event.Character == 'i'          
           rueda2=0;
           rueda1=0;
           rueda3=1;
        elseif event.Character == 'k'
           rueda2=0;
           rueda1=0;
           rueda3=-1;
        elseif event.Character == 'j'          
           rueda2=-1;
           rueda1=-1;
           rueda3=-1;
        elseif event.Character == 'l'
           rueda2=1;
           rueda1=1;
           rueda3=1;
        else 
           rueda2=0;
           rueda1=0;
           rueda3=0;
        end
        disp(fprintf('rueda1= %d', rueda1));
        disp(fprintf('rueda2= %d', rueda2));
        disp(fprintf('rueda3= %d', rueda3));
    end
  end

Answer 1

[per isakson]

I made a couple of changes to you function and tested.

• "Output argument "rueda1" (and maybe others) not assigned during call" &nbsp the reason is that the function executes to the end before you hit any key. One way to avoid that error is to add [rueda1,rueda2,rueda3] = deal( nan ); % <<<<<<<<< edit
• prinfig is a nested function. It shares the variables rueda1,rueda2,rueda3 with its parent function. Thus function printfig(~,event) % <<<<<<<<< edit without output arguments

Test:

    >> [rueda1,rueda2,rueda3]=testkeyboard;
    w
    rueda1= 1     9
    rueda2= 0     9
    rueda3= 0     9
    k
    rueda1= 0     9
    rueda2= 0     9
    rueda3= -1    10
    >>  [rueda1,rueda2,rueda3]
    ans =
       NaN   NaN   NaN
    >>

where

    function [rueda1,rueda2,rueda3]=testkeyboard

      figure('KeyPressFcn',@printfig);
      [rueda1,rueda2,rueda3] = deal( nan ); % <<<<<<<<< edit

      function  printfig(~,event)           % <<<<<<<<< edit
      % Callback to parse keypress event data to print a figure
          if event.Character == 'w'
             rueda2=0;
             rueda1=1;
             rueda3=0;
          elseif event.Character == 's'
  ...
          end
          disp( event.Character )           % <<<<<<<<< edit
          disp(fprintf('rueda1= %d', rueda1));

&nbsp

Regarding comment 1

"but they are always in NaN" &nbsp Yes that is the expected behavior. The function, testkeyboard, is run once and returns [nan,nan,nan] to the base (/caller) workspace. In response to pressing a key the nested function printfig is executed. It updates the values in the workspace of testkeyboard, but that's all. Adding the lines

        assignin( 'caller', 'rueda1', rueda1 )
        assignin( 'caller', 'rueda2', rueda2 )
        assignin( 'caller', 'rueda3', rueda3 )

at the end of printfig will update the variable values in the base workspace. However, I don't think that helps.

"create a figure of a "robot", and move it with testkeyboard"

IMO: You need to step back and do some basic design. There is hardly a way to achieve the goal by small changes to your code.

Model-View-Controller is an ambitious approach. (There exists variants and different meaning of the term.) See

• Model View Control Pattern using GUIDE by Chris Schwarz
• MVC in Matlab

A nested-function-approach

• GUI Examples using Nested Functions by Steven Lord
• I would start with something like this

    function  my_robot
        rueda = nan(3,1); % shared variable
        create_view
        function create_view
             figure('KeyPressFcn',@catch_keystroke);
        end
        function update_view
        end
        function catch_keystroke
            update_view
        end
    end

[francisco]

thank you, that was very usefull, but i need to change the value of rueda1,rueda2 and rueda3, but they are always in NaN. this is the program caller of testkeyboard:

This create a figure of a "robot", and move it with testkeyboard

can you help me? Thanks

    % x = 0;
    y = 0;
    tita = 0;
    samplingTime = 0.1;
    R = 0.15;
    r = 0.05;
    %figure(1), hold on, grid on
    [a,b,c]= testkeyboard;
    xlabel('X (metros)');
    ylabel('Y (metros)');
    xlim([-5 10]);
    ylim([-5 10]);
    legend
    for cont = 1:inf
        robot = hexarobo(x,y,tita);
        rueda1=a; rueda2=b; rueda3=c;
        B=[ -sin(tita + 1.570796327) cos(tita + 1.570796327) R;
            -sin(tita + 3.665191429) cos(tita + 3.665191429) R;
            -sin(tita + 5.759586532) cos(tita + 5.759586532) R];
        x = x + r*B(1,:)*[rueda1; rueda2; rueda3];
        y = y + r*B(2,:)*[rueda1; rueda2; rueda3];
        tita = tita + r*B(3,:)*[rueda1; rueda2; rueda3];
        pause(samplingTime); %Tiempo de pausa obligatorio
        delete(robot); %borro objeto "robot" para ...con movimiento
    end