How to get the exact position of a plotted point?

2011 8 17
4 个回答
回答已采纳
更新时间：2021 5 15
20 次查看（30 天）

1 个投票

Hi,
I've plotted a graph and additionally marked a specific point. A 'ButtonDownFcn' is assigned to the point, to enable user interaction.
By clicking onto the point I would like to receive its exact x and y coordinates.
My approach:
function getPlotPointCoord()
clc;
figure(1);
x = -2*pi:0.05:+2*pi;
subplot(1,2,1);
hold on;
plot(x, sin(x));
% plot point at (x=0, y=0)
plot(0, sin(0), 'bx', 'ButtonDownFcn', @getPoint);
function getPoint(varargin)
currentPoint = get(gca, 'CurrentPoint');
fprintf('Hit Point! Coordinates: %f, %f \n', ...
currentPoint(1), currentPoint(3));
end
end
The call _get(gca, 'CurrentPoint') for instance returns the following values:
Hit Point! Coordinates: 0.000000, 0.002924
Hit Point! Coordinates: 0.000000, 0.002924
Hit Point! Coordinates: 0.000000, 0.002924
Hit Point! Coordinates: -0.106952, -0.008772
Hit Point! Coordinates: 0.106952, -0.014620
Is there a way to receive the true values (x=0, y=0) of the 'button' instead of the current (most likely) mouse-coordinates?
Thank you!

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 采纳的回答

Fangjun Jiang
Fangjun Jiang 2011-8-17

2 个投票

What do you mean? You want the x/y value of the data points? You can get that from menu Tools->Data Cursor and then click along the curve.

8 个评论
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BF83
BF83 2011-8-17
Thanks for your answer.
I don't want to use the data cursor in this special case. I wonder if there is a easy way to obtain these coordinates just by using the 'ButtonDownFcn' assigned to the specific point.
Fangjun Jiang
Fangjun Jiang 2011-8-17
Okay, then I guess you could write a few more lines to compare the current point to see which data point is the closest.
Fangjun Jiang
Fangjun Jiang 2011-8-17
Wait a minute! Can't you do this?!
plot(0, sin(0), 'bx', 'ButtonDownFcn', 'disp([0,sin(0)])');
BF83
BF83 2011-8-17
Ok! Perhaps I can pass the coordinates to a function, for instance to @getPoint?
Fangjun Jiang
Fangjun Jiang 2011-8-17
Yes. Like:
plot(0, sin(0), 'bx', 'ButtonDownFcn', 'getPoint(0,sin(0))')
BF83
BF83 2011-8-17
Okay, great. I'm sure that it will solve my problem. I'm gonna test it tomorrow.
Thank you for coming up with this easy and elegant solution.
Trishank Sharma
Trishank Sharma 2018-7-8
编辑：Trishank Sharma 2018-7-8
Hi what if I have a set of 60 points (n=60), where x and y are real and imaginary parts of a complex number Z. Can I know the point number (the 'n'th point) beside the coordinates or do I have to do it manually?

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更多回答（3 个）

BF83
BF83 2011-8-18

0 个投票

A working example for completion:
function getPlotPointCoord()
clc;
figure(1);
x = -2*pi:0.05:+2*pi;
subplot(1,2,1);
hold on;
plot(x, sin(x));
plot(0, sin(0), 'bx', 'ButtonDownFcn', {@getPoint, 0, sin(0)});
function getPoint(src, eventdata, x, y)
currentPoint = get(gca, 'CurrentPoint');
fprintf('Hit Point! Mouse Coordinates: %f, %f \n', ...
currentPoint(1), currentPoint(3));
fprintf('Hit Point! Real Coordinates: %f, %f \n', x, y);
end
end
Tarami Readus
Tarami Readus 2019-1-23

0 个投票

Where in the code does he add the marker, and to what specific point? I would like to know how to do that
Adam Albayati
Adam Albayati 2019-5-8

0 个投票

function getPlotPointCoord()
clc;
figure(1);
x = -2*pi:0.05:+2*pi;
subplot(1,2,1);
hold on;
plot(x, sin(x));
% plot point at (x=0, y=0)
plot(0, sin(0), 'bx', 'ButtonDownFcn', @getPoint);
function getPoint(varargin)
currentPoint = get(gca, 'CurrentPoint');
fprintf('Hit Point! Coordinates: %f, %f \n', ...
currentPoint(1), currentPoint(3));
end
end

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