Sort and limit number of bars to display on bargraph

问题

I have a dataset of traffic violations and want to display only the top 10 violations per month on a bargraph. Can I limit the number of bars after sorting values to display only the top 10? There are 42 different column names of traffic violations.

month_jan = df[df.MonthName == "Jan"]
month_jan[feature_cols].sum().sort_values(ascending=0).plot(kind='bar')

Feature_cols is a list of all 42 column names that correspond to traffic violations.

Thanks!

回答1:

This will work:

month_jan[feature_cols].sum().sort_values(ascending=0)[:10].plot(kind='bar')

回答2:

Series objects have a .head method, just like DataFrames (docs). This allows you to select the top N items very elegantly with data.head(N). Here's a complete working example:

import pandas as pd

df = pd.DataFrame({
    'feature1': [0, 1, 2, 3],
    'feature2': [2, 3, 4, 5],
    'MonthName': ['Jan', 'Jan', 'Jan', 'Feb']
})
feature_cols = ['feature1', 'feature2']

month_jan = df[df.MonthName == "Jan"]
top10 = month_jan[feature_cols].sum().sort_values(ascending=0).head(10)
top10.plot(kind='bar')

来源：https://stackoverflow.com/questions/38338396/sort-and-limit-number-of-bars-to-display-on-bargraph