How to get x y coordinates from a Matplotlib scatterplot graphic - python-3.x

Question

I have a Widget into my GUI hosting a scatterplot graphic. I managed to include a pick event but am not able to get the x y coordinate by clicking a plot only the print('yahoo') works. My code is based on the following article: see link (section: Simple picking example).
How can I get the coordinates of the point (e.g. x=20 and y=50 which is one my five points) by clicking the point on the scatterplot?
Front-end code:
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(595, 393)
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
self.gridLayout.setObjectName("gridLayout")
self.pushButton = QtWidgets.QPushButton(self.centralwidget)
self.pushButton.setMaximumSize(QtCore.QSize(100, 16777215))
self.pushButton.setObjectName("pushButton")
self.gridLayout.addWidget(self.pushButton, 0, 0, 1, 1)
self.widget = QtWidgets.QWidget(self.centralwidget)
self.widget.setMinimumSize(QtCore.QSize(0, 200))
self.widget.setStyleSheet("background-color: rgb(255, 255, 255);")
self.widget.setObjectName("widget")
self.gridLayout.addWidget(self.widget, 0, 1, 1, 1)
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtWidgets.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 595, 21))
self.menubar.setObjectName("menubar")
MainWindow.setMenuBar(self.menubar)
self.statusbar = QtWidgets.QStatusBar(MainWindow)
self.statusbar.setObjectName("statusbar")
MainWindow.setStatusBar(self.statusbar)
self.retranslateUi(MainWindow)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
def retranslateUi(self, MainWindow):
_translate = QtCore.QCoreApplication.translate
MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
self.pushButton.setText(_translate("MainWindow", "PushButton"))
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
MainWindow = QtWidgets.QMainWindow()
ui = Ui_MainWindow()
ui.setupUi(MainWindow)
MainWindow.show()
sys.exit(app.exec_())
Back-end code:
import sys
import matplotlib.pyplot as plt
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QApplication, QWidget, QSizePolicy
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
from matplotlib.figure import Figure
from front_end import Ui_MainWindow
class Graph_init(FigureCanvas):
def __init__(self, parent=None):
fig = Figure()
fig.patch.set_facecolor("None")
self.axes = fig.add_subplot(111)
self.compute_initial_figure()
FigureCanvas.__init__(self, fig)
self.setParent(parent)
FigureCanvas.setSizePolicy(self, QSizePolicy.Expanding, QSizePolicy.Expanding)
FigureCanvas.updateGeometry(self)
FigureCanvas.mpl_connect(self, 'pick_event', self.onclick)
def onclick(self, event):
print('yahoo')
thisline = self.event.artist
xdata = thisline.get_xdata()
ydata = thisline.get_ydata()
class Graph_populate(Graph_init):
def compute_initial_figure(self):
x = [10,20,30,40,50]
y = [100,50,150,200,75]
size = [1000,2000,3000,5000,2000]
self.axes.scatter(x,y,s=size,color='blue', picker=1)
self.axes.patch.set_facecolor('None')
class GUI(QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
super(GUI, self).__init__(parent)
self.setupUi(self)
self.sc = Graph_populate(self.widget)
self.gridLayout.addWidget(self.sc, 0, 1, 1, 1)
if __name__ == '__main__':
app = QApplication(sys.argv)
prog = GUI()
prog.showMaximized()
sys.exit(app.exec_())
Thank you

Answer 1

You are plotting a scatterplot. Hence you may have a look at the third part of the pick_event_demo, where a scatterplot is treated.
The idea would be to get the index of the picked datapoint and take the data at that index out to obtain the coordinates.
def onclick(self, event):
ind = event.ind[0]
data = event.artist.get_offsets()
xdata, ydata = data[ind,:]
print ((xdata, ydata))
Note that those are the coordintes of the data point, not those of the mouseclick (which is how I understand the question).