pyqtgraph/examples/ScatterPlot.py

# -*- coding: utf-8 -*-
import sys, os
## Add path to library (just for examples; you do not need this)
sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..'))

from pyqtgraph.Qt import QtGui, QtCore
import pyqtgraph as pg
import numpy as np

app = QtGui.QApplication([])
mw = QtGui.QMainWindow()
mw.resize(800,800)
view = pg.GraphicsLayoutWidget()  ## GraphicsView with GraphicsLayout inserted by default
mw.setCentralWidget(view)
mw.show()

## create four areas to add plots
w1 = view.addPlot()
w2 = view.addViewBox()
w2.setAspectLocked(True)
view.nextRow()
w3 = view.addPlot()
w4 = view.addPlot()
print("Generating data, this takes a few seconds...")

## There are a few different ways we can draw scatter plots; each is optimized for different types of data:


## 1) All spots identical and transform-invariant (top-left plot). 
## In this case we can get a huge performance boost by pre-rendering the spot 
## image and just drawing that image repeatedly.

n = 300
s1 = pg.ScatterPlotItem(size=10, pen=pg.mkPen(None), brush=pg.mkBrush(255, 255, 255, 120))
pos = np.random.normal(size=(2,n), scale=1e-5)
spots = [{'pos': pos[:,i], 'data': 1} for i in range(n)] + [{'pos': [0,0], 'data': 1}]
s1.addPoints(spots)
w1.addItem(s1)

## Make all plots clickable
lastClicked = []
def clicked(plot, points):
    global lastClicked
    for p in lastClicked:
        p.resetPen()
    print("clicked points", points)
    for p in points:
        p.setPen('b', width=2)
    lastClicked = points
s1.sigClicked.connect(clicked)



## 2) Spots are transform-invariant, but not identical (top-right plot). 
## In this case, drawing is as fast as 1), but there is more startup overhead
## and memory usage since each spot generates its own pre-rendered image.

s2 = pg.ScatterPlotItem(size=10, pen=pg.mkPen('w'), pxMode=True)
pos = np.random.normal(size=(2,n), scale=1e-5)
spots = [{'pos': pos[:,i], 'data': 1, 'brush':pg.intColor(i, n), 'symbol': i%5, 'size': 5+i/10.} for i in range(n)]
s2.addPoints(spots)
w2.addItem(s2)
w2.setRange(s2.boundingRect())
s2.sigClicked.connect(clicked)


## 3) Spots are not transform-invariant, not identical (bottom-left). 
## This is the slowest case, since all spots must be completely re-drawn 
## every time because their apparent transformation may have changed.

s3 = pg.ScatterPlotItem(pxMode=False)   ## Set pxMode=False to allow spots to transform with the view
spots3 = []
for i in range(10):
    for j in range(10):
        spots3.append({'pos': (1e-6*i, 1e-6*j), 'size': 1e-6, 'brush':pg.intColor(i*10+j, 100)})
s3.addPoints(spots3)
w3.addItem(s3)
s3.sigClicked.connect(clicked)


## Test performance of large scatterplots

s4 = pg.ScatterPlotItem(size=10, pen=pg.mkPen(None), brush=pg.mkBrush(255, 255, 255, 20))
pos = np.random.normal(size=(2,10000), scale=1e-9)
s4.addPoints(x=pos[0], y=pos[1])
w4.addItem(s4)
s4.sigClicked.connect(clicked)



## Start Qt event loop unless running in interactive mode.
if sys.flags.interactive != 1:
    app.exec_()