How to set xlim in seaborn barplot?

Question

I have created a barplot for given days of the year and the number of people born on this given day (figure a). I want to set the x-axes in my seaborn barplot to xlim = (0,365) to show the whole year.
But, once I use ax.set_xlim(0,365) the bar plot is simply moved to the left (figure b).

This is the code:

#data
df = pd.DataFrame()
df['day'] = np.arange(41,200)
df['born'] = np.random.randn(159)*100

#plot
f, axes = plt.subplots(4, 4, figsize = (12,12))
ax = sns.barplot(df.day, df.born, data = df, hue = df.time, ax = axes[0,0], color = 'skyblue')
ax.get_xaxis().set_label_text('')
ax.set_xticklabels('')
ax.set_yscale('log')
ax.set_ylim(0,10e3)
ax.set_xlim(0,366)
ax.set_title('SE Africa')

How can I set the x-axes limits to day 0 and 365 without the bars being shifted to the left?

Asked By: Thomas

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Source

Answer 1

IIUC, the expected output given the nature of data is difficult to obtain straightforwardly, because, as per the documentation of seaborn.barplot:

This function always treats one of the variables as categorical and draws data at ordinal positions (0, 1, … n) on the relevant axis, even when the data has a numeric or date type.

This means the function seaborn.barplot creates categories based on the data in x (here, df.day) and they are linked to integers, starting from 0.

Therefore, it means even if we have data from day 41 onwards, seaborn is going to refer the starting category with x = 0, making for us difficult to tweak the lower limit of x-axis post function call.

The following code and corresponding plot clarifies what I explained above:

import pandas as pd 
import numpy as np 
import matplotlib.pyplot as plt
import seaborn as sns

# data
rng = np.random.default_rng(101)
day = np.arange(41,200)
born = rng.integers(low=0, high=10e4, size=200-41)

df = pd.DataFrame({"day":day, "born":born})

# plot
f, ax = plt.subplots(figsize=(4, 4))

sns.barplot(data=df, x='day', y='born', ax=ax, color='b')
ax.set_xlim(0,365)
ax.set_xticks(ticks=np.arange(0, 365, 30), labels=np.arange(0, 365, 30))
ax.set_yscale('log')
ax.set_title('SE Africa')
plt.tight_layout()
plt.show()

I suggest using matplotlib.axes.Axes.bar to overcome this issue, although handling colors of the bars would be not straightforward compared to sns.barplot(..., hue=..., ...) :

# plot
f, ax = plt.subplots(figsize=(4, 4))

ax.bar(x=df.day, height=df.born) # instead of sns.barplot
ax.get_xaxis().set_label_text('')
ax.set_xlim(0,365)
ax.set_yscale('log')
ax.set_title('SE Africa')
plt.tight_layout()
plt.show()

Answered By: medium-dimensional

How to set xlim in seaborn barplot?

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