Add style details to a barplot

Question

I have prepared the following plot:

x = [1, 2, 3, 4, 5, 6]
y = [-0.015, 0.386, -0.273, -0.091, 0.955, 1.727]
errors = [0.744, 0.954, 0.737, 0.969, 0.848, 0.460]

plt.figure(figsize=(8, 4))
plt.bar(x, y, yerr=errors, align='center', alpha=0.5, color='grey')
plt.xticks((0, 1, 2, 3, 4, 5, 6, 7), ('', 'I1', 'I2', 'I3', 'I4', 'I5', 'I6', ''))
plt.ylim((-3, 3))
plt.show()

I have a couple of questions:

How do i add the bottom and top dashes in the error segment?
I would like to color the background green if y > 0.8, yellow if -0.8 <= y <= 0.8, red if y < -0.8. How can I do it?

Asked By: LJG

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Source

Answer 1

To set the horizontal lines, you need to use capsize=n. Larger the n, wider the horizontal lines. You can set the background color using axvspan() and select color based on the value of y. Below is the updated code. I changed y value of one to show the red color…

x = [1, 2, 3, 4, 5, 6]
y = [-0.015, 0.386, -0.273, -0.091, -0.955, 1.727]
errors = [0.744, 0.954, 0.737, 0.969, 0.848, 0.460]

plt.figure(figsize=(8, 4))
ax=plt.bar(x, y, yerr=errors, align='center', alpha=0.5, color='grey', capsize=5)
plt.xticks((0, 1, 2, 3, 4, 5, 6, 7), ('', 'I1', 'I2', 'I3', 'I4', 'I5', 'I6', ''))
plt.ylim((-3, 3))
for i in range(1,7):
    if y[i-1]  > 0.8:
        color = 'green'
    elif y[i-1]  > -0.8:
        color = 'yellow'
    else:
        color = 'red'
    plt.axvspan(i-0.5, i+.5, facecolor=color, alpha=0.3)
plt.show()

EDIT:

As requested, you are looking for horizontal ranges. So, you would need to use axhspan(). To bring the gray to solid, change alpha to 1 and you will need to bring the bars to the front using zorder(). I also added edgecolor='gray' to keep the look of a fully solid bar. Code is below…

plt.figure(figsize=(8, 4))
ax=plt.bar(x, y, yerr=errors, align='center', alpha=1, color='grey', edgecolor='gray',capsize=10, zorder=2)
plt.xticks((0, 1, 2, 3, 4, 5, 6, 7), ('', 'I1', 'I2', 'I3', 'I4', 'I5', 'I6', ''))
plt.ylim((-3, 3))

plt.axhspan(0.8, plt.gca().get_ylim()[1], facecolor='green', alpha=0.3, zorder=1)
plt.axhspan(-0.8, 0.8, facecolor='yellow', alpha=0.3, zorder=1)
plt.axhspan(plt.gca().get_ylim()[0], -0.8, facecolor='red', alpha=0.3, zorder=1)
plt.show()

Answered By: Redox

Add style details to a barplot

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