# How can i exactly click on a point that has drawed on a plot using ginput ?

3 vues (au cours des 30 derniers jours)
Le Dung le 11 Jan 2019
Commenté : Jan le 4 Nov 2019
Hello!
My problem is:
I have had some points on a figure use plot command with this command lines:
figure;
hold on
x = [1 2 3 4 5]
y = [7 8 9 10 11]
for i = 1:5
plot(x(i),y(i),'*','MarkerSize',12,'Color','r')
end
% Retrieve coordinate of points
[xx,yy] = ginput(length(x))
Now, I want to use ginput() or getPoint() to click on anypoint in the figure.
But, It is difficult to click on a point exxactly.
For example, i want to click on first point that has x = 1 and y = 7. But, when i trying to click on it to retrieve its coordinate, what matlab returns is that i expect (x = 1,y = 7)..
How can i do?????
Thank you so much!
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Jan le 11 Jan 2019
Why not? Why can't you click on the wanted points? Which problem do you want to solve? To determine the point nearest to the location you click on? To do this, clicking on a specific location is not needed. Why do you think clicking on an exact location is useful? Remember that the point [1.000000000000000, 7.000000000000000] might not be exactly represented by a pixel, but of course you can select a single pixel only. This means that clicking on a specific coordinate is not possible or at least extremely hard using a massive zooming. So why do you want to do this at all?
Le Dung le 11 Jan 2019
Modifié(e) : Le Dung le 11 Jan 2019
yes.
if i draw a line that contains two points, for example, (4,5) and (10,5). that means i created a horizontal line has 6 units ( for example meter). but if i click on point (4.05,5.1) and point (10.07,5.02) when use ginput(), for example, so, the line that created is having a difference in length from the line i want to create.
and, why do i want to do this?
yes. actually, i‘m building a GUI.
i have two GUIs. main GUI and subGUi. there is a axes on main GUi (gui1) and there are edittext and push button on sub gui( gui2).
when i click on push button on gui2, matlab will draw two points on axes on GUI1 with data (coordinates of points) gets from edittext. and then, i want to draw a line contains two points that drawed previously on axes.
i mean i want to use ginput() click on point 1 and then click on point 2. after click on point 2, matlab will draw a line contains two points
do you understand that i wrote.
because my english is not well

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### Réponse acceptée

Jan le 11 Jan 2019
Modifié(e) : Jan le 11 Jan 2019
Considering my comment, my answer is:
You can't. You would need a massive zooming to try to do so. Remember, that [1.000000000000000, 7.000000000000000] is not necessarily represented by a pixel on the screen, but selecting a pixel is the maximum achievable resolution.
The solution is to adjust your needs: What about finding the point nearest to the selected pixel?
What about using the ButtonDownFcn of the drawn points instead of ginput?
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Timon Rayis le 30 Oct 2019
@Jan
Is that an alternate for ginput?
Jan le 4 Nov 2019
The ButtonDownFcn is a property of the object e.g. created by plot or line. Example:
AxesH = axes;
LineH = line(1:10, rand(1,10), 'ButtonDownFcn', {@myCallback, AxesH});
function myCallback(LineH, EventData, AxesH)
disp(AxesH.CurrentPoint)
end

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