Change Order on X-Axis for Matplotlib chart

Question

I created a chart in matplotlib using python and the x-axis is the days of the week (Mon-Sun). When the data was plotted though, the x-axis is not arranged Mon-Sun.

Is there way I can re-order the x-axis to have it be formatted this way?

or is there a way I can re-order the dataset? It is a csv file that is being read using the panda dataframe

Example Data: (lives in csv: './data/Days_Summary.csv')

Day         Value

 Monday      56        
 Tuesday     23    
 Wednesday   34     
 Thursday     56     
  Friday      58     
 Saturday     70      
  Sunday      43      

Code:

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
df=pd.read_csv('./data/Days_Summary.csv')
days_values=df.groupby(['day'])['day'].count().plot(kind='bar')
plt.xlabel('Day')
plt.ylabel('Values')
plt.show()

Answer 1

Use .loc to set the day order:

field = "Day"
day_order = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
ax = df.set_index(field).loc[day_order].plot(kind="bar", legend=False)
ax.set_ylabel("Value")

Note: Using groupby() and count() will not give you the values in the Value field, but will instead count the number of rows in each group. In this case, you'll just get a count of 1 for each day. Hence this answer assumes that you actually want to plot the values in Value for each day.