Change the appearance of the plotted line depending on the amount of zoom.

zoom_adaptive_line.py

"""
Change the appearance of the plotted line depending on the amount of zoom.
Line properties changed include: line width, line color and marker type

Code derived from the clippedline example
http://matplotlib.sourceforge.net/examples/pylab_examples/clippedline.html
"""
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.lines import Line2D

class ZoomAdaptiveLine(Line2D):
    """
    Change the appearence of the line depending on the the axes view limits
    (this example assumes x is sorted)
    """

    def __init__(self, ax, *args, **kwargs):
        Line2D.__init__(self, *args, **kwargs)
        self.color_orig = self.get_color()

    def draw(self, renderer):
        '''overloaded `draw` method of Line2D'''
        xlim = self.axes.get_xlim()
        ind0, ind1 = np.searchsorted(self._x, xlim)
        N = ind1-ind0 # number of currenly displayed points
        
        if N<100:
            self.set_marker('d')
            self.set_color('g')
            self.set_lw(1)
        elif N<1000:
            self.set_marker('+')
            self.set_color('c')
            self.set_lw(2)
        else:
            self.set_marker('')
            self.set_color(self.color_orig)
            self.set_lw(2)
        
        Line2D.draw(self, renderer)


fig = plt.figure()
ax = fig.add_subplot(111)
# Generate some sine wave :
t = np.arange(0.0, 100.0, 0.01)
s = np.sin(2*np.pi*t)

# Create the derrived Line2D object:
line = ZoomAdaptiveLine(ax, t, s, color='b', ls='-', lw=1)

# Create the plot:
ax.add_line(line)
ax.set_xlim(10,30)
ax.set_ylim(-1.1,1.1)
ax.set_title('Zoom in to see the change of linestyle')
plt.show()