points id and scatter markers distance adjustment in figure.

% for example;

x=[1000;1100;1200];
y=[2000;2100;2200];
points_id={'p100';'p200';'p300'};
figure(1),scatter(x, y, 'b^');grid on;
text(x, y+10, points_id);   %it writes points id, a bit above scatter.

x=[10000;11000;12000];
y=[20000;21000;22000];
points_id={'p100';'p200';'p300'};
figure(1),scatter(x, y, 'b^');grid on;
text(x, y+10, points_id);

It writes the IDs a bit above scatter point markers but this time it isn't sufficient, because the coordinates are 10 times bigger than the previous one. When the user applies a zoom towards the points, the points IDs move farther away from the markers. Is there any way to adjust the distance between markers and ids each time automatically, and fix the points ID position when the user applies a zoom?

Answer 1

[Geoff Hayes]

Yes, it just depends on how you feel about using global variables. (This is just something I looked at for the first time, so there may be more elegant approaches.) You can capture zoom events and adjust your text widgets based on whether the user is zooming in or out. Suppose you take your block of code (from above) and place it in a new function called moving_ids:

 function moving_ids

 close all;

 global GRID_TEXT_HANDLES;  % global var of all text handles (for ids)
 global X_COORDS;           % global var of the x coordinates
 global Y_COORDS;           % global var of the y coordinates

 X_COORDS=[10000;11000;12000];  % need this info in post-zoom callback
 Y_COORDS=[20000;21000;22000];  % need this info in post-zoom callback
 points_id={'p100';'p200';'p300'};
 figure(1),scatter(X_COORDS, Y_COORDS, 'b^');grid on;

 % save handles to text/ids for post-zoom callback
 GRID_TEXT_HANDLES = text(X_COORDS, Y_COORDS+10, points_id); 

 % get the figure's zoom mode object
 h = zoom;

 % set the pre-zoom callback
 set(h,'ActionPreCallback',@prezoom);

 % set the post-zoom callback
 set(h,'ActionPostCallback',@postzoom);

In the above, we have set the framework to capture zoom events in the figure. Now you need to define the callbacks. The pre-zoom callback will be used to capture the limits (prior to zoom) of each axis:

 function prezoom(obj,event_obj)
 % obj         handle to the figure clicked on
 % event_obj   object containing struct of event data 
 %             (same as the event data of the 
 %             'ActionPreCallback' callback)

 global PREZOOM_AXIS_X_LIMITS;  % global var of the pre-zoom x-axis limits
 global PREZOOM_AXIS_Y_LIMITS;  % gloval var of the pre-zoom y-axis limits

 PREZOOM_AXIS_X_LIMITS = get(event_obj.Axes,'XLim');
 PREZOOM_AXIS_Y_LIMITS = get(event_obj.Axes,'YLim');

We are going to use the above pre-zoom limits to determine how the label position should be adjusted relative to the marker during the post-zoom. Now we handle the post-zoom action which will be used to adjust the text for each marker:

 function postzoom(obj,event_obj)
 % obj         handle to the figure clicked on
 % event_obj   object containing struct of event data 
 %             (same as the event data of the 
 %             'ActionPreCallback' callback)

 global PREZOOM_AXIS_X_LIMITS;
 global PREZOOM_AXIS_Y_LIMITS;
 global GRID_TEXT_HANDLES;
 global X_COORDS;
 global Y_COORDS;

 % get the post-zoom limits for each axis
 PSTZOOM_AXIS_X_LIMITS = get(event_obj.Axes,'XLim');
 PSTZOOM_AXIS_Y_LIMITS = get(event_obj.Axes,'YLim');

 % determine the difference in the limits (for y only since in your code,
 % the x-coordinate of the marker and label are identical)
 prezoomYDiff = abs(PREZOOM_AXIS_Y_LIMITS(2) - PREZOOM_AXIS_Y_LIMITS(1));
 pstzoomYDiff = abs(PSTZOOM_AXIS_Y_LIMITS(2) - PSTZOOM_AXIS_Y_LIMITS(1));

 % adjust each label
 for i=1:length(Y_COORDS)

    % get the y-coordinate only for the marker
    y = Y_COORDS(i);

    % get the text handle for the label
    txtHandle = GRID_TEXT_HANDLES(i);

    % get the 3D position of the label
    txtPos    = get(txtHandle,'Position');

    % calculate the difference (between the marker and label) in y only
    yDiff     = abs(txtPos(2)-y);

    % set the new difference/range (from marker to label) to be at least 1
    % and at most 10 (chosen as per original placement) using the ratio of
    % post-zoom y-axis limit wrt pre-zoom y-axis limit
    newYDiff  = min(10,max(1,pstzoomYDiff/prezoomYDiff*yDiff));

    % set the new position for the label relative to the marker
    set(txtHandle,'Position', [txtPos(1) y+newYDiff txtPos(3)]);
end

If you choose to have a different x-coordinate (for the label) then the above code would have to be adjusted to do something similar for the changing x. Hope that this helps!