Appending Matrix

Hello everyone,

I have this code that writes zeros to a matrix based on the length of a listbox and popupmenu options. 1s are written to the matrix based on selections from the popupmenu and listbox:

      function [] = pop_ex()
      % Help goes here.
      S.fh = figure('units','pixels',...
                    'position',[200 400 320 340],...
                    'menubar','none',...
                    'name','slider_ex',...
                    'numbertitle','off',...
                    'resize','off');
      S.pp = uicontrol('style','pop',...
                       'unit','pix',...
                       'position',[20 20 80 40],...
                       'string',{'one','two','three','four'},...
                       'callback',@pp_call); 
      S.ls = uicontrol('style','list',...
                       'unit','pix',...
                       'position',[20 80 80 40],...
                       'min',0,'max',5,...
                       'string',{'lone','ltwo','lthree','lfour','lfive','lsix'});

        guidata(S.fh,S)  
        function [] = pp_call(varargin) 
        % Callback for the popup.
        S = guidata(gcbf);
        A =            zeros(length(get(S.pp,'string')),length(get(S.ls,'string'))); %create matrix A, fill with zeros based on length of popup and list items
        A(get(S.pp,'val'),get(S.ls,'val')) = 1;
      %write 1s for selected items
        A
        %output A

The code works however, I want to append the matrix instead of creating a new one each time.

[B_Richardson]

%This line creates the matrix and fills it with zeros

A = zeros(length(get(S.pp,'string')),length(get(S.ls,'string')));

%this line writes 1s to the matrix based on the currently selected items from the listbox and popupmenu

A(get(S.pp,'val'),get(S.ls,'val')) = 1;

So the idea is upon multiple calls to this popupmenu callback (eventually this will be in a button separate from the popupmenu)

append A instead of creating a new A everytime

Answer 1

[Fangjun Jiang]

So it's not really append A, rather it is setting one element of A to 1 one at a time. What you need is to load A from guidata at the beginning of the callback function. save A to guidata at the end of the callback function. The setting of A to all zeros is better to put in the CreateFcn callback.

[B_Richardson]

%1st callback

A =

1 1 0 0 0 0

0 0 0 0 0 0

0 0 0 0 0 0

0 0 0 0 0 0

%2nd

A =

0 0 0 0 0 0

0 1 1 0 0 0

0 0 0 0 0 0

0 0 0 0 0 0

%3rd

A =

0 0 0 0 0 0

0 0 0 0 0 0

0 0 0 1 1 0

0 0 0 0 0 0

%4th

A =

0 0 0 0 0 0

0 0 0 0 0 0

0 0 0 0 0 0

0 0 0 0 1 1

%But this is actually what I want to accomplish

A =

1 1 0 0 0 0

0 1 1 0 0 0

0 0 1 1 0 0

0 0 0 0 1 1

[B_Richardson]

"So it's not really append A, rather it is setting one element of A to 1 one at a time."

%No, actually it is appending A. See above example

"What you need is to load A from guidata at the beginning of the callback function."

%Not sure if that is gonna work seeing as througout my program A changes length based on the listbox options

"save A to guidata at the end of the callback function."

%Yes, I agree

"The setting of A to all zeros is better to put in the CreateFcn callback."

%Why is that?

[Fangjun Jiang]

That is what I meant. In your example, A doesn't change size. In every call back, two elements are changed. So in your callback function, you don't want to re-set it to be all zeros. The initialization of A is better to be put in the CreatFcn callback. Then, in this callback, every time you need to load the previous value of A first, and then change some of its elements and then save it back. That is the right programming flow, right?

[B_Richardson]

I understand now. Thank you!