'''
Example to create boxes from error using PatchCollection
'''

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import PatchCollection
from matplotlib.patches import Rectangle

# Number of data points
n = 5

# Dummy data
x = np.arange(0, n, 1)
y = np.random.rand(n)*5.

# Dummy errors (above and below)
xerr = np.random.rand(2, n)
yerr = np.random.rand(2, n)

# Create figure and axes
fig, ax = plt.subplots(1)


def make_error_boxes(ax, xdata, ydata, xerror, yerror, fc='r', ec='None', alpha=0.5):

    # Create list for all the error patches
    errorboxes = []

    # Loop over data points; create box from errors at each point
    for xc, yc, xe, ye in zip(xdata, ydata, xerror.T, yerror.T):
        rect = Rectangle((xc-xe[0], yc-ye[0]), xe.sum(), ye.sum())
        errorboxes.append(rect)

    # Create patch collection with specified colour/alpha
    pc = PatchCollection(errorboxes, facecolor=fc, alpha=alpha, edgecolor=ec)

    # Add collection to axes
    ax.add_collection(pc)

    # Plot errorbars
    ax.errorbar(xdata, ydata, xerr=xerror, yerr=yerror, fmt='None', ecolor='k')


# Call function to create error boxes
make_error_boxes(ax, x, y, xerr, yerr)

plt.show()