Change the numer rows of a uitable in MATLAB gui automatically using GUIDE?

How to create an option (text box) to enter a number to automatically change the number rows of a uitable in MATLAB gui using GUIDE?

Answer 1

[Walter Roberson]

uit = uitable('Data', [0 0 0]);
FirstN = @(Matrix, N) Matrix(1:N, :);
ChopN = @(Matrix, N) FirstN([Matrix; zeros(N, size(Matrix,2))], N);
uicontrol('style', 'edit', 'Callback', @(src, event) set(uit, 'data', ChopN(get(uit, 'data'), str2double(get(src, 'string'))));

[Nikhil Tamhankar]

Hello, sorry but I completely new to MATLAB and GUIDE programming, so could you please elaborate and explain the steps you have provided?

[Walter Roberson]

You need a uitable to start with. For the code later to work properly, you cannot just initialize it with [] -- you have to initialize it with something with the same number of columns as you are going to use.

The uicontrol() call sets up the uicontrol text area that you want to control the number of rows in the table.

The Callback on the uicontrol is run when the user presses return inside the text area or clicks in the text area (possibly editing the text) and clicks outside the area.

The 'Callback' property of the uicontrol says which routine is to be run when the callback is triggered.

The callback to be run is the anonymous function

@(src, event) set(uit, 'data', ChopN(get(uit, 'data'), str2double(get(src, 'string'))

This is a function that takes two parameters, src and event and executes the code

set(uit, 'data', ChopN(get(uit, 'data'), str2double(get(src, 'string')))

using those two parameters. MATLAB automatically supplies those two parameters for every callback. The second of them is not important at the moment. The first parameter is the handle to the graphics object whose callback is being executed.

The code get(src, 'string') is taking that handle to the current uicontrol and fetching the String property, which is the property that stores the text that has been entered into the field.

str2double() of the string property converts the text representing a number into the number -- so if the user had entered the characters 127 into the field then the uicontrol would have stored that as '127' and you need to convert the text '127' into the number 127; the str2double does that.

For the code

get(uit, 'data')

you have to look back and see that I assigned the handle of the uitable to the variable uit . So get(uit, 'data') is fetching the current data property of the uitable.

Now, ChopN() is being called, with the first argument being the data pulled from the uitable, and the second argument being the number pulled from the edit field.

ChopN = @(Matrix, N) FirstN([Matrix; zeros(N, size(Matrix,2))], N);

tells us that ChopN is a function with two parameters. zeros(N, size(Matrix,2)) is called, which creates a block of zeros that is N rows high by the number of columns already in Matrix ("size of its second dimension"). That block of zeros is put onto the bottom of the existing block of data by way of the [Matrix; zeros...] operation. We know that the result must be at least N rows tall, and possibly taller, because of the N rows of zeros we put on the bottom. Now we call FirstN with that larger matrix together with N

FirstN = @(Matrix, N) Matrix(1:N, :);

tells us that FirstN is a function with two parameters. The function expects a matrix as input, and it extracts the first N rows of the matrix.

So ChopN adding N rows of zeros to the bottom and then calls FirstN to take the first N rows of that larger matrix. As noted above we know that there are at least N rows, so we know that extracting out the first N of the result will always be possible.

If you think about this a bit, what this combination of operations is doing is:

• if the existing matrix was larger than the user specified in the edit field, then only the size specified by the user will be kept and the rest will be thrown away
• if the existing matrix was smaller than the user specified in the edit field, then the matrix will be padded with exactly enough rows of zeros so that the result is the size the user requested.

set(uit, 'data', ....)

The result of this "adjust to be exactly the right length" operation is passed to set the data field of the uitable we defined earlier. So the uitable will be adjusted to the length the user specified.

To be honest, there are clearer ways of writing this code, by writing a real function to do the work instead of using anonymous functions. But writing a real function would require that I instruct you about how to write real functions and where they have to be stored and so on.

[Nikhil Tamhankar]

Thank you so much...I will try to understand and implement your suggestions.

[Vinayak Appasaheb Bhatte]

I have a slider and a edit box with slider callback shown below

global val

val = get(hObject, 'Value');

set(handles.edit3, 'String', num2str(val))

Should I initialize src with handles.edit3? Also I created a uitable, but nothing is changing in the table with respect to edit box and slider.

Thank you

[Walter Roberson]

No, you should not initialize that. But if you prefer you could rewrite the callback

@(src, event) set(uit, 'data', ChopN(get(uit, 'data'), str2double(get(src, 'string'))

as instead

@(hObject, event) set(uit, 'data', ChopN(get(uit, 'data'), str2double(get(hObject, 'string'))

"Also I created a uitable, but nothing is changing in the table with respect to edit box and slider."

Unfortunately you did not happen to post your code for us to look at.

[Vinayak Appasaheb Bhatte]

Thank you so much for the response, below is my code for uitable

function uitable1_CellEditCallback(hObject, eventdata, handles)

src = handles.edit3;

uit = uitable1('Data', [0 0 0]);

FirstN = @(Matrix, N) Matrix(1:N, :);

ChopN = @(Matrix, N) FirstN([Matrix; zeros(N, size(Matrix,2))], N);

uicontrol('style', 'edit', 'Callback', @(src, event) set(uit, 'data', ChopN(get(uit, 'data'), str2double(get( handles.edit3, 'string')))));

[Walter Roberson]

Why are you creating a new uicontrol every time you run the cell edit callback ?

What is the function named "uitable1" ? It looks similar to what you would use if you were creating a new uitable, but why would you create a new uitable every time you had a callback for an existing uitable?

I suggest you create your uitable in GUIDE. Then in the OpenFcn callback (not a CreateFcn callback),

set(handles.uitable1,  'Data', [0 0 0]);

and set the CellEditCallback property for uitable1 to

function uitable1_CellEditCallback(hObject, eventdata, handles)

    FirstN = @(Matrix, N) Matrix(1:N, :);
    ChopN = @(Matrix, N) FirstN([Matrix; zeros(N, size(Matrix,2))], N);

   set(hObject, 'Data', ChopN(get(hObject, 'Data'), str2double(get( handles.edit3, 'string'))) )

[Vinayak Appasaheb Bhatte]

Thank you so much for your quick response. I appreciate it.

I did as you said, But when I enter a number say around 10 in my edit box and when I click outside the edit box I don't see the 10 rows filled automatically.

[Walter Roberson]

You programmed a cell edit callback, which is a callback that activates when the user edits data in the uitable. If you want the change to happen when the user edits the edit box, then

function edit3_Callback(hObject, eventdata, handles)
  FirstN = @(Matrix, N) Matrix(1:N, :);
  ChopN = @(Matrix, N) FirstN([Matrix; zeros(N, size(Matrix,2))], N);

   set(handles.uitable1, 'Data', ChopN(get(handles.uitable1, 'Data'), str2double(get( hObject, 'string'))) )

[Vinayak Appasaheb Bhatte]

Thanks a lot @Walter for your kind explanation, I did work finally.

Answer 2

[Image Analyst]

You can just assign the data to it and it will automatically adjust its size to handle/display all the rows and columns in your data matrix:

handles.uitable1.Data = yourData;

Or, you can just click on the little icon in the Columns entry in the Property Inspector, which you can bring up in GUIDE by double clicking on the table control.

[Nikhil Tamhankar]

I will put a text box in the gui to enter the value of number of rows, and then i want the uitable to change according to the value entered...how can I do this?

[Image Analyst]

Basically get the string from the edit box

contentsString = handles.edit1.String;

Then parse contentsString to get what you want and expect - a row or whole matrix of whatever - and load that into yourData and then use the code I originally gave you:

handles.uitable1.Data = yourData;

[Nikhil Tamhankar]

Thank you sir. Will try to understand your suggestion and try to implement it.