How can the edge colors of individual matplotlib histograms be set? - matplotlib

Question

I've got a rough and ready function that can be used to compare two sets of values using histograms:
I want to set the individual edge colors of each of the histograms in the top plot (much as how I set the individual sets of values used for each histogram). How could this be done?
import os
import datavision
import matplotlib.pyplot
import numpy
import shijian
def main():
a = numpy.random.normal(2, 2, size = 120)
b = numpy.random.normal(2, 2, size = 120)
save_histogram_comparison_matplotlib(
values_1 = a,
values_2 = b,
label_1 = "a",
label_2 = "b",
normalize = True,
label_ratio_x = "measurement",
label_y = "",
title = "comparison of a and b",
filename = "histogram_comparison_1.png"
)
def save_histogram_comparison_matplotlib(
values_1 = None,
values_2 = None,
filename = None,
directory = ".",
number_of_bins = None,
normalize = True,
label_x = "",
label_y = None,
label_ratio_x = None,
label_ratio_y = "ratio",
title = "comparison",
label_1 = "1",
label_2 = "2",
overwrite = True,
LaTeX = False,
#aspect = None,
font_size = 20,
color_1 = "#3861AA",
color_2 = "#00FF00",
color_3 = "#7FDADC",
color_edge_1 = "#3861AA", # |<---------- insert magic for these
color_edge_2 = "#00FF00", # |
alpha = 0.5,
width_line = 1
):
matplotlib.pyplot.ioff()
if LaTeX is True:
matplotlib.pyplot.rc("text", usetex = True)
matplotlib.pyplot.rc("font", family = "serif")
if number_of_bins is None:
number_of_bins_1 = datavision.propose_number_of_bins(values_1)
number_of_bins_2 = datavision.propose_number_of_bins(values_2)
number_of_bins = int((number_of_bins_1 + number_of_bins_2) / 2)
if filename is None:
if title is None:
filename = "histogram_comparison.png"
else:
filename = shijian.propose_filename(
filename = title + ".png",
overwrite = overwrite
)
else:
filename = shijian.propose_filename(
filename = filename,
overwrite = overwrite
)
values = []
values.append(values_1)
values.append(values_2)
bar_width = 0.8
figure, (axis_1, axis_2) = matplotlib.pyplot.subplots(
nrows = 2,
gridspec_kw = {"height_ratios": (2, 1)}
)
ns, bins, patches = axis_1.hist(
values,
color = [
color_1,
color_2
],
normed = normalize,
histtype = "stepfilled",
bins = number_of_bins,
alpha = alpha,
label = [label_1, label_2],
rwidth = bar_width,
linewidth = width_line,
#edgecolor = [color_edge_1, color_edge_2] <---------- magic here? dunno
)
axis_1.legend(
loc = "best"
)
bars = axis_2.bar(
bins[:-1],
ns[0] / ns[1],
alpha = 1,
linewidth = 0, #width_line
width = bins[1] - bins[0]
)
for bar in bars:
bar.set_color(color_3)
axis_1.set_xlabel(label_x, fontsize = font_size)
axis_1.set_ylabel(label_y, fontsize = font_size)
axis_2.set_xlabel(label_ratio_x, fontsize = font_size)
axis_2.set_ylabel(label_ratio_y, fontsize = font_size)
#axis_1.xticks(fontsize = font_size)
#axis_1.yticks(fontsize = font_size)
#axis_2.xticks(fontsize = font_size)
#axis_2.yticks(fontsize = font_size)
matplotlib.pyplot.suptitle(title, fontsize = font_size)
if not os.path.exists(directory):
os.makedirs(directory)
#if aspect is None:
# matplotlib.pyplot.axes().set_aspect(
# 1 / matplotlib.pyplot.axes().get_data_ratio()
# )
#else:
# matplotlib.pyplot.axes().set_aspect(aspect)
figure.tight_layout()
matplotlib.pyplot.subplots_adjust(top = 0.9)
matplotlib.pyplot.savefig(
directory + "/" + filename,
dpi = 700
)
matplotlib.pyplot.close()
if __name__ == "__main__":
main()

Answer 1

You may simply plot two different histograms but share the bins.
import numpy as np; np.random.seed(3)
import matplotlib.pyplot as plt
a = np.random.normal(size=(89,2))
kws = dict(histtype= "stepfilled",alpha= 0.5, linewidth = 2)
hist, edges,_ = plt.hist(a[:,0], bins = 6,color="lightseagreen", label = "A", edgecolor="k", **kws)
plt.hist(a[:,1], bins = edges,color="gold", label = "B", edgecolor="crimson", **kws)
plt.show()

Answer 2

Use the lists of Patches objects returned by the hist() function.
In your case, you have two datasets, so your variable patches will be a list containing two lists, each with the Patches objects used to draw the bars on your plot.
You can easily set the properties on all of these objects using the setp() function. For example:
a = np.random.normal(size=(100,))
b = np.random.normal(size=(100,))
c,d,e = plt.hist([a,b], color=['r','g'])
plt.setp(e[0], edgecolor='k', lw=2)
plt.setp(e[1], edgecolor='b', lw=3)