Callback function not forwarding the variables.

Question

Adil Ali 2019-11-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/491098-callback-function-not-forwarding-the-variables

编辑： Guillaume 2019-11-14

I am developing a tool that simulates the function of a LiDAR given certain parameters. The simulation results in a plot (2D for now) that shows the pattern of the laser as well as the points captured on a given surface. I would like to be able to draw a rectangle (for now) on the 2D graph and be able to compute the number of points within the box. I have displayed a pushbutton on the graph that lets the user to start drawing the box if pressed.

The code allows the user to draw a box on the graph using ginput(2). But I am stuck in getting the number of points within the box. I am working with inpolygon() but getting errors. I appreaciate your help.

X = laser1_pts(:,1);                                                       % x - coordinates of all the points --> assign to X
Y = laser1_pts(:,2);                                                       % y - coordinates of all the points --> assign to Y
Z = laser1_pts(:,3);                                                       % z - coordinates of all the points --> assign to Z
scatter(X,Y,ptSz,'r','filled');
%% Create button to trigger polygon selection to eventually compute point density within polygon                                                                                                                           
hb = uicontrol('Style','togglebutton');                                    %% Create a toggle button
set(hb,'position',[1 1,120,20])                                            %% Setting position of the button [1PixelRight 1PixelUp, width, height]
set(hb,'String', 'Pt Density')                                             %% Add text on the button
set(hb, 'callback', {@computeDensity,X,Y})
function computeDensity(hb,eventdata, handles,X,Y)
%polygon = zeros(4,2);
while get(hb,'Value')  
    [plyX, plyY] = ginput(2);
    width = abs(plyX(1) - plyX(2));
    height = abs(plyY(1) - plyY(2)); 
    h = rectangle('Position',[plyX(1) plyY(1) width height]);
    [in,on] = inpolygon(X,Y,plyX,plyY);
    inon = in | on;
    idx = find(inon(:));
    xcoord = X(idx);
    ycoord = Y(idx);
    PointsInSelection = numel(xcoord);
   
    pause(5);
    delete(h);
    
end

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Adam 2019-11-14

在 MATLAB Online 中打开

Well, in your case since it is a programmatic GUI you would need to initialise something like

guidata( hb, struct );

after creating the uicontrol to create a structure in the first place. This is only useful if you wish the callback to return values.

Then

handles = guidata( hb );

would retrieve this structure within your callback.

guidata( hb, handles )

would then write the structure back into hb, which is obviously only useful if you have actually changed the struct in some way, such as adding or editing a field.

Adil Ali 2019-11-14

Could you paste these commands in my code so I have a better understanding of what you are saying? I tried including your commands according to my understanding but it doesnt seem to be working.

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Answer 1

Stijn Haenen 2019-11-14

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/491098-callback-function-not-forwarding-the-variables#answer_401517

在 MATLAB Online 中打开

If you have the edges of the square you can maybe use this example to get the number of points inside the square.

x=1:100;
y=100:-1:1;
scatter(x,y)
xmin=20;
xmax=50;
ymin=70;
ymax=80;
points_x=x(x<xmax&x>xmin&y>ymin&y<ymax);
points_y=y(x<xmax&x>xmin&y>ymin&y<ymax);
num_points=numel(points_x);
hold on
scatter(points_x,points_y,'r')