Mendapatkan koordinat titik data terdekat pada plot matplotlib

Saya menggunakan matplotlibdengan NavigationToolbar2QT. Bilah alat menunjukkan posisi kursor. Tapi saya ingin kursor terkunci ke titik data terdekat (ketika cukup dekat) atau hanya menunjukkan koordinat titik data terdekat. Bisakah itu entah bagaimana diatur?

Jika Anda bekerja dengan sejumlah besar poin, saya menyarankan Anda untuk menggunakan CKDtrees:

import matplotlib.pyplot as plt
import numpy as np
import scipy.spatial

points = np.column_stack([np.random.rand(50), np.random.rand(50)])
fig, ax = plt.subplots()
coll = ax.scatter(points[:,0], points[:,1])
ckdtree = scipy.spatial.cKDTree(points)

Saya refactored kpie'smenjawab di sini sedikit. Setelah ckdtreedibuat, Anda dapat mengidentifikasi titik terdekat secara instan dan berbagai jenis informasi tentangnya dengan sedikit usaha:

def closest_point_distance(ckdtree, x, y):
    #returns distance to closest point
    return ckdtree.query([x, y])[0]

def closest_point_id(ckdtree, x, y):
    #returns index of closest point
    return ckdtree.query([x, y])[1]

def closest_point_coords(ckdtree, x, y):
    # returns coordinates of closest point
    return ckdtree.data[closest_point_id(ckdtree, x, y)]
    # ckdtree.data is the same as points

Tampilan posisi kursor interaktif. Jika Anda ingin koordinat titik terdekat ditampilkan di Bilah Alat Navigasi:

def val_shower(ckdtree):
    #formatter of coordinates displayed on Navigation Bar
    return lambda x, y: '[x = {}, y = {}]'.format(*closest_point_coords(ckdtree, x, y))

plt.gca().format_coord = val_shower(ckdtree)
plt.show()

Menggunakan acara. Jika Anda ingin jenis interaktivitas lain, Anda dapat menggunakan acara:

def onclick(event):
    if event.inaxes is not None:
        print(closest_point_coords(ckdtree, event.xdata, event.ydata))

fig.canvas.mpl_connect('motion_notify_event', onclick)
plt.show()

Kode berikut akan mencetak koordinat titik yang paling dekat dengan mouse saat Anda mengklik.

import matplotlib.pyplot as plt
import numpy as np
np.random.seed(19680801)
N = 50
x = np.random.rand(N)
y = np.random.rand(N)
fig,ax = plt.subplots()
plt.scatter(x, y)
points = list(zip(x,y))
def distance(a,b):
    return(sum([(k[0]-k[1])**2 for k in zip(a,b)])**0.5)
def onclick(event):
    dists = [distance([event.xdata, event.ydata],k) for k in points]
    print(points[dists.index(min(dists))])
fig.canvas.mpl_connect('button_press_event', onclick)
plt.show()

Anda bisa subkelas NavigationToolbar2QTdan menimpa mouse_movepawang. The xdatadan ydataatribut berisi posisi mouse saat ini di koordinat petak. Anda dapat mengambil itu ke titik data terdekat sebelum melewati acara ke kelas basismouse_move penangan .

Contoh lengkap, dengan menyoroti titik terdekat dalam plot sebagai bonus:

import sys

import numpy as np

from matplotlib.backends.qt_compat import QtWidgets
from matplotlib.backends.backend_qt5agg import FigureCanvas, NavigationToolbar2QT
from matplotlib.figure import Figure


class Snapper:
    """Snaps to data points"""

    def __init__(self, data, callback):
        self.data = data
        self.callback = callback

    def snap(self, x, y):
        pos = np.array([x, y])
        distances = np.linalg.norm(self.data - pos, axis=1)
        dataidx = np.argmin(distances)
        datapos = self.data[dataidx,:]
        self.callback(datapos[0], datapos[1])
        return datapos


class SnappingNavigationToolbar(NavigationToolbar2QT):
    """Navigation toolbar with data snapping"""

    def __init__(self, canvas, parent, coordinates=True):
        super().__init__(canvas, parent, coordinates)
        self.snapper = None

    def set_snapper(self, snapper):
        self.snapper = snapper

    def mouse_move(self, event):
        if self.snapper and event.xdata and event.ydata:
            event.xdata, event.ydata = self.snapper.snap(event.xdata, event.ydata)
        super().mouse_move(event)


class Highlighter:
    def __init__(self, ax):
        self.ax = ax
        self.marker = None
        self.markerpos = None

    def draw(self, x, y):
        """draws a marker at plot position (x,y)"""
        if (x, y) != self.markerpos:
            if self.marker:
                self.marker.remove()
                del self.marker
            self.marker = self.ax.scatter(x, y, color='yellow')
            self.markerpos = (x, y)
            self.ax.figure.canvas.draw()


class ApplicationWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self._main = QtWidgets.QWidget()
        self.setCentralWidget(self._main)
        layout = QtWidgets.QVBoxLayout(self._main)
        canvas = FigureCanvas(Figure(figsize=(5,3)))
        layout.addWidget(canvas)
        toolbar = SnappingNavigationToolbar(canvas, self)
        self.addToolBar(toolbar)

        data = np.random.randn(100, 2)
        ax = canvas.figure.subplots()
        ax.scatter(data[:,0], data[:,1])

        self.highlighter = Highlighter(ax)
        snapper = Snapper(data, self.highlighter.draw)
        toolbar.set_snapper(snapper)


if __name__ == "__main__":
    qapp = QtWidgets.QApplication(sys.argv)
    app = ApplicationWindow()
    app.show()
    qapp.exec_()