Annotate Percentage of Group within a Seaborn CountPlot - python-3.x

Question

The below code gets the percentage of all collisions. However, I want to get the percentage within a group. E.G. Mid-Block (not related to intersection) has 2 labels, a 1(red) or a 2(green/blue). Currently, the percentages next to those bars are percentages of the whole (bar count / all collisions), but I need to display the percentage within just one y-axis label. E.G. for Mid-block (not related to intersection), bar count / all collisions within mid-block (not related to intersection). I do not know how to do this, so if someone could point me in the right direction or give me some code that I could study to understand, I'd be very grateful.
Thank you so much for your time.
plt.style.use('ggplot')
plt.figure(figsize = (20, 15))
ax = sb.countplot(y = "JUNCTIONTYPE", hue = "SEVERITYCODE", data = dfm)
plt.title('Number of Persons vs. Number of Collisions by Severity', fontsize = 30)
plt.xlabel('Number of Collisions', fontsize = 24)
plt.ylabel('Number of Persons', fontsize = 24)
plt.tick_params(labelsize=18);
plt.legend(fontsize = 18, title = "Severity", loc = 'lower right')
plt.text(5, 6, "Figure 8: Number of persons plotted against the number of collisions grouped by severity", fontsize = 16)
# labels = [item.get_text() for item in ax.get_yticklabels()]
# labels[0] = 'No'
# labels[1] = 'Yes'
# ax.set_yticklabels(labels)
for p in ax.patches:
width = p.get_width()
height = p.get_height()
x, y = p.get_xy()
ax.annotate(int(width),
((x + width), y),
xytext = (30, -25),
fontsize = 18,
color = '#000000',
textcoords = 'offset points',
ha = 'right',
va = 'center')
for p in ax.patches:
width = p.get_width()
height = p.get_height()
x, y = p.get_xy()
totals = []
for i in ax.patches:
totals.append(i.get_width())
total = sum(totals)
ax.text(width + 0.3, y + 0.38,
str(
round((width/total) * 100, 2))
+ '%',
fontsize=18)

Answer 1

You could pre-calculate the per-group percentage points and use the order in which seaborn / matplotlib draws the bars to reference them.
import seaborn as sns
import matplotlib.pyplot as plt
import pandas as pd
titanic = sns.load_dataset('titanic')
# prepare the dataset
df = (titanic
.groupby(["embark_town", "survived"])
.size()
.reset_index()
.replace({"survived": {0:"no", 1:"yes"}})
.rename(columns={0:"count"}))
# calculate survival % per town of embarkation
df["percent"] = (df
.groupby("embark_town")
.apply(lambda x: x["count"] / x["count"].sum()).values)
# sort the dataframe to match the drawing order
df.sort_values(by=["survived", "embark_town"], inplace=True)
# visualisation
plt.style.use('ggplot')
fig = sns.catplot(
x="count", y="embark_town", hue="survived",
kind="bar", data=df, height=4, aspect=2)
for i, bar in enumerate(fig.ax.patches):
height = bar.get_height()
fig.ax.annotate(
# reference the pre-calculated row in the dataframe
f"{df.iloc[i, 3] :.0%}",
xycoords="data",
xytext=(20, -15),
textcoords="offset points",
xy=(bar.get_width(), bar.get_y()),
ha='center', va='center')
# make space for annonations
plt.margins(x=0.2)
plt.show()