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matlab 2019b - bug in data tips accuracy

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Gal Maman
Gal Maman on 17 Nov 2019
Commented: Adam Danz on 19 Aug 2021
Hi,
I'm using 2019b and I can't get the accurate value of a point in the graph using data tips.
Attached is an example.
Is there a way to fix this?
Thanks,
Gal

Accepted Answer

Adam Danz
Adam Danz on 17 Nov 2019
Edited: Adam Danz on 19 Aug 2021
The values reported in the datatips are accurate, judging from the png image. Precision seems to be the issue, not accuracy. Note that your x and y axis ticks are x10^4. The reason the two x-values appear to be 77020 is probably because the data tips are not showing more precise values (ie, 77020.48930).
Here are two method To change the precision of datatip values.
Method 1: custom update function
Adapt this demo to your needs. The custom update function is not called when manually adding datatips with the datatip() function (available in Matlab r2019a and later).
% Create a plot
figure()
ph = plot(magic(5).*7000+rand(1), 'o');
% Specify a custom update function to your data cursor object
dcm = datacursormode(gcf);
set(dcm, 'UpdateFcn', @customDataCursorUpdateFcn, 'Enable', 'On');
% Here's the function that specifies 5 decimal places
function txt = customDataCursorUpdateFcn(~, event)
pos = event.Position;
txt = {sprintf('X: %.5f', pos(1)), sprintf('Y: %.5f', pos(2))};
end % <- may not be needed
Method 2: using DataTipTemplate
Unlike method 1, this method is supported when manually adding datatips with datatip(). Since datatip content differs between objects, you may need to adapt this demo to your needs. The demo changes the x and y values which are assumed to be in the first and second rows of the datatip. This is applied to all line objects in vector ph.
% Create plot
figure()
ph = plot(magic(5).*7000+rand(1), 'o');
% Specify precision of X (first row) and Y (second row) values in dataip
for i = 1:numel(ph)
ph(i).DataTipTemplate.DataTipRows(1).Format = '%.5f'; % X
ph(i).DataTipTemplate.DataTipRows(2).Format = '%.5f'; % Y
end
Show example datatip
datatip(ph(1), ph(1).XData(4), ph(1).YData(4));
  4 Comments
Adam Danz
Adam Danz on 19 Aug 2021
Method 2 added to answer on 19-Aug 2021.

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