
Hi, I needed some help tweaking a multicolored line with matplotlib. I adopted tacaswell's answer on StackOverflow at http://stackoverflow.com/a/30125761/3566440When I do the steps exactly like its explained in the answer, I am able to replicate it. However, my case is a bit different. I have a dataframe with timeseries as it's index, and 'perc99_99' as a set of Zscores. I modified the SO answer to the best of my knowledge and this is what the code looks like:
fig, ax = plt.subplots()
# Index of dataframe = timestamps x = day_avg_zscore.index.values # Z score of 99th percentiles y = day_avg_zscore['perc99_99'].values
# Threshold at Zscore = 2, using helper function
lc = threshold_plot(ax, x, y, 2, 'k', 'r') ax.axhline(2, color='k', ls='') lc.set_linewidth(3)
plt.show()
I left the helper function intact: import numpy as np import matplotlib.pyplot as plt from matplotlib.collections import LineCollection from matplotlib.colors import ListedColormap, BoundaryNorm
def threshold_plot(ax, x, y, threshv, color, overcolor): """ Helper function to plot points above a threshold in a different color
Parameters  ax : Axes Axes to plot to x, y : array The x and y values
threshv : float Plot using overcolor above this value
color : color The color to use for the lower values
overcolor: color The color to use for values over threshv
""" # Create a colormap for red, green and blue and a norm to color # f' < 0.5 red, f' > 0.5 blue, and the rest green cmap = ListedColormap([color, overcolor]) norm = BoundaryNorm([np.min(y), threshv, np.max(y)], cmap.N)
# Create a set of line segments so that we can color them individually # This creates the points as a N x 1 x 2 array so that we can stack points # together easily to get the segments. The segments array for line collection # needs to be numlines x points per line x 2 (x and y) points = np.array([x, y]).T.reshape(1, 1, 2) segments = np.concatenate([points[:1], points[1:]], axis=1)
# Create the line collection object, setting the colormapping parameters. # Have to set the actual values used for colormapping separately. lc = LineCollection(segments, cmap=cmap, norm=norm) lc.set_array(y)
ax.add_collection(lc) ax.set_xlim(np.min(x), np.max(x)) ax.set_ylim(np.min(y)*1.1, np.max(y)*1.1) return lc
Here's what I get as an output: What am I missing?
I'm using Anaconda Python2.7 and Jupyter Notebook.
Thank you!
 Deep

Sent from my phone. Please forgive typos and other forms of brevity.
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