[FIXED] Stacked bar chart with custom gradient coloring

Issue

Here's what I came up with by plotting thick line segments. The coloration is blue, with varying alpha, 0 < alpha < 1.

My workaround doens't work as I'd like because I don't have a legend (I want a legend that shows a gradient of the blue at varying alpha).

Additionally, I've found that matplotlib scales funny. There should be no overlap of the bars, but if I adjust the window size, the gap between the line segments will change.This is the same figure as the earlier one, just after I've resized the figure window with my mouse.

I'm not sure if there's a better way to go about accomplishing this, or if there's a different package I can use. Here's the snippet of code that I'm using.

import matplotlib.pyplot as plt
x1  =[0, 19, 39, 46, 60, 79]
x2 = [19, 39, 46, 60, 79, 90]
alpha_list = [-0.8402, -0.6652, 0.0, -0.5106, -0.8074, 0.0]
plt.figure()
for idx,x in enumerate(x1):
    plt.plot([x1[idx],x2[idx]],[0,0],color = 'blue',alpha=alpha_list[idx],linewidth =20)
plt.show()

Solution

I suppose alpha is just a workaround for using different shades of blue? In that case the Blues colormap can be used instead.
Several lines can be plotted using a LineCollection.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection

x1  =[0, 19, 39, 46, 60, 79]
x2 = [19, 39, 46, 60, 79, 90]
alpha_list = [-0.8402, -0.6652, 0.0, -0.5106, -0.8074, 0.0]

verts = np.dstack((np.c_[x1, x2], np.zeros((len(x1), 2))))

fig, ax = plt.subplots()
lc = LineCollection(verts, linewidth=40, cmap="Blues_r", array=np.array(alpha_list))
ax.add_collection(lc)

ax.autoscale()
ax.set_ylim(-1,1)
fig.colorbar(lc)
plt.show()

Answered By - ImportanceOfBeingErnest