How to set data cursor to max value programically?

Question

Rohit Bhoi 2016-4-11

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评论： yijun guo 2022-7-11

Hello, I want to set data cursor to max value how to do it programically? I used following code but its not working properly. Its how cursor for max value but doesn't set value...

x = 0:pi/20:2*pi; 
y = sin(x*0.3)+2*cos(2*x);
[max_val,index] = max(y);
plot(x,y); hold on; 
plot(x(index),max_val,'ks','markerfacecolor',[0 0 0]);
text(x(index)-0.5,max_val-0.3,['Max: ', num2str(max_val)])

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Answer 1

Baltam 2016-4-11

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编辑：Walter Roberson 2016-4-11

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x = 0:pi/20:2*pi; 
y = sin(x*0.3)+2*cos(2*x);
[max_val,index] = max(y);
h =figure; hPlot = plot(x,y);
cursorMode = datacursormode(h);
hDatatip = cursorMode.createDatatip(hPlot);
pos = [x(index) y(index) 0];
set(hDatatip, 'Position', pos)         
updateDataCursors(cursorMode)

Is this what you need?

Kind regards,

Baltam

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Scotty Neally 2020-4-9

I've tried using this code and it works great in version R2019b with a caveat: when I set the position of the datatip it is highly dependant on the figure window size. I noticed that my X-axis value was a few points off and tried to determine whether my index was incorrect. It turns out that if you rescale the figure window before sending the set(hDatatip,'Position',[X Y Z]); command you will get completely different results based on the figure window size at the time....

Perhaps this is covered in the undocumented section of matlab (https://undocumentedmatlab.com/articles/controlling-plot-data-tips)? I haven't had a chance to read through in detail yet.

Thanks!

-Scotty

Scotty Neally 2020-4-28

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Was just able to solve my problem with a combination of using dummy plot commands to re-focus the datacursor to the correct axes before creating a new datatip. Also, using the Cursor.DataIndex was infinitely more reliable for me instead of using the built-in search function to find the location when "position" is specified:

plot(app.UIAxes2,[],[]); %refocus datacursormode on UIAxes2
plot(app.UIAxes1,[],[]); %refocus datacursormode on UIAxes1
hDatatip.Cursor.DataIndex = 501; %set datatip position based on data index 

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Answer 2

Adam Danz 2020-10-29

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编辑：Adam Danz 2020-10-29

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Update: as of r2019b you can use datatip(__) to programmatically place a data tip.

Demo:

fig = figure();

ax1 = subplot(1,2,1);

h1 = plot(magic(5));

datacursormode on

datatip(h1(2), 2, 5);

subplot(1,2,2)

h2 = plot(rand(10), 'sb');

datatip(h2(3),'DataIndex',5);

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Adam Danz 2022-7-7

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@yijun guo

h1 = plot(magic(5)) creates 5 handles, one for each column of data

h1 = plot(magic(5))

h1 =

5×1 Line array: Line Line Line Line Line

close % close figure, we don't need it here

h1(2) selects the second line object.

yijun guo 2022-7-11

thanks a lot

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Answer 3

Leandro de Oliveira 2019-9-28

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编辑：Leandro de Oliveira 2019-9-28

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Hi guys, I did a new version because it doesn't worked propoerly to me, the data tip do not get updated, so there it is:

First of all, I get this code HERE.

clc; clear all; close all;
%-------------------------------------------------------------------------%
s = tf('s');
%-------------------------------------------------------------------------%
G = (s+40)/((s^2)+(1.2*s)+4);
%-------------------------------------------------------------------------%
lw = 2;
h1 = figure(1);
    [mag, fase, w] = bode(G);
    hObj = semilogx(w, 20*log10(squeeze(mag)), 'linewidth', lw);
    [max_val, index] = max(mag);
    cursorMode = datacursormode(h1);
    hDatatip = cursorMode.createDatatip(hObj);
    pos = [w(index) 20*log10(mag(index))];
    set(get(hDatatip, 'DataCursor'), 'DataIndex', index, 'TargetPoint', pos);
    set(hDatatip, 'Position', pos);
    updateDataCursors(cursorMode);
    grid on
%-------------------------------------------------------------------------%   