I have been writing a program to show quotes from Yahoo Finance service. After a few searches I know Matplotlib has matplotlib.widgets.Cursor to do the task, here is the example code. It’s not the kind of cursor we want, the cursor in such program must to snap its horizontal line to the price in figure.
So this snap version example could fit the need. This cursor manually draw the cursor. It works fine if your figure only have one or two data lines. If you use something like matplotlib.finance.CandleSticks, which plot many things on your figure. You will see the lag of movement of your cursor.
The first example has a way to deal with that, it’s called Blit, you can read more about it at this page. Basically, you save the rendered image, every time you need to draw your cursor, you restore that saved image, then you draw your cursor. That would save a lot of time. There is a another example code for Blit.
I wrote my own example as following:
#!/usr/bin/env python import datetime import matplotlib matplotlib.use('GTKAgg') from matplotlib.figure import Figure from matplotlib.backends.backend_gtkagg import FigureCanvasGTKAgg as FigureCanvas import matplotlib.finance as finance import matplotlib.mlab as mlab from numpy import searchsorted, array try: import pygtk pygtk.require("2.0") except: print "You need to install pyGTK or GTKv2 or set your PYTHONPATH correctly" sys.exit(1) import gtk # Modified from http://matplotlib.sourceforge.net/examples/pylab_examples/cursor_demo.html class SnaptoCursor: def __init__(self, ax, x, y, useblit=True): self.ax = ax self.lx = None self.ly = None self.x = x self.y = y self.bg = None self.useblit = useblit def mouse_move(self, event): if not event.inaxes: return ax = event.inaxes minx, maxx = ax.get_xlim() miny, maxy = ax.get_ylim() if self.useblit and self.bg is None: self.bg = ax.figure.canvas.copy_from_bbox(ax.bbox) ax.figure.canvas.restore_region(self.bg) x, y = event.xdata, event.ydata indx = searchsorted(self.x, [x])[0] if indx == len(self.x): indx = len(self.x) - 1 x = self.x[indx] y = self.y[indx] # update the line positions if self.lx is not None: self.lx.set_data((minx, maxx), (y, y)) self.ly.set_data((x, x), (miny, maxy)) else: color = 'b-' if self.useblit else 'r-' self.lx, = ax.plot((minx, maxx), (y, y), color) # the horiz line self.ly, = ax.plot((x, x), (miny, maxy), color) # the vert line if self.useblit: ax.draw_artist(self.lx) ax.draw_artist(self.ly) ax.figure.canvas.blit(ax.bbox) else: ax.figure.canvas.draw() def create_figure(quotes): f = Figure(figsize=(5,4), dpi=100) a = f.add_subplot(111) canvas = FigureCanvas(f) # a gtk.DrawingArea canvas.set_size_request(800,300) a.xaxis_date() finance.candlestick(a, quotes, width=0.5) return f def main(): win = gtk.Window() win.connect('destroy', gtk.main_quit) win.set_title('Cursors') vbox = gtk.VBox() win.add(vbox) # Get data from Yahoo Finance enddate = datetime.date.today() startdate = enddate + datetime.timedelta(days=-72) quotes = finance.quotes_historical_yahoo('GOOG', startdate, enddate) qa = array(quotes) f = create_figure(quotes) a = f.gca() vbox.pack_start(gtk.Label('No Blit'), False, False) vbox.pack_start(f.canvas) cursor1 = SnaptoCursor(a, qa[:,0], qa[:,2], useblit=False) f.canvas.mpl_connect('motion_notify_event', cursor1.mouse_move) f = create_figure(quotes) a = f.gca() vbox.pack_start(gtk.Label('Use Blit'), False, False) vbox.pack_start(f.canvas) cursor2 = SnaptoCursor(a, qa[:,0], qa[:,2], useblit=True) f.canvas.mpl_connect('motion_notify_event', cursor2.mouse_move) win.show_all() gtk.main() if __name__ == '__main__': main()
[1] | http://xs1144.xs.to/xs1144/09434/matplotlib-cursor371.png is gone. |
[2] | http://xs1144.xs.to/xs1144/09434/matplotlib-cursor661.png is gone. |
0 comments:
Post a Comment
Note: Only a member of this blog may post a comment.