如何使条形图注释水平居中? [英] How to horizontally center a bar plot annotation?

问题描述

我正在创建这样的条形图:

  gender = ['M'，'F']数字= [男，女]条= plt.bar(性别，数字，宽度= 0.1，底部=无，align ='居中'，数据=无)对于范围内的我(len(numbers)):plt.annotate(str(numbers [i])，xy =(gender [i]，numbers [i]))plt.show() 

我想使用 plt.annotate 在栏的顶部写入确切的值.但是，该值打印在右侧.可以将其移到中心吗?

解决方案

• 为了指定注释的水平对齐方式，请使用 ha 参数

  • I am creating a bar chart like this:

    gender = ['M', 'F']
    numbers = [males,females]
    bars = plt.bar(gender, numbers, width=0.1, bottom=None, align='center', data=None)
    for i in range(len(numbers)):
        plt.annotate(str(numbers[i]), xy=(gender[i],numbers[i]))
    plt.show()
    

    I want to use plt.annotate to write the exact value on the top of the bar. However, the value is printed towards the right side. Is it possible to move it to the center?

    解决方案

    • In order to specify the horizontal alignment of the annotation, use the ha parameter
      • matplotlib: Text Properties & Layout
      • matplotlib: Annotations
      • matplotlib.pyplot.annotate
    • As per the suggestion from JohanC
      • A trick is to use f'{value}\n' as a string and the unmodified value (or numbers) as y position, together with va='center'.
      • This also works with plt.text. Alternatively, plt.annotation accepts an offset in 'points' or in 'pixels'.

    Option 1

    • From lists of values & categories

    import matplotlib.pyplot as plt
    
    gender = ['M', 'F']
    numbers = [1644, 1771]
    
    plt.figure(figsize=(12, 6))
    bars = plt.bar(gender, numbers, width=0.1, bottom=None, align='center', data=None)
    for i in range(len(numbers)):
        plt.annotate(f'{numbers[i]}\n', xy=(gender[i], numbers[i]), ha='center', va='center')
    

    Option 2

    • From a pandas.DataFrame
    • Use pandas.DataFrame.iterrows to extract the x and y location needed for the annotations.
      • x being the categorical 'gender' value
      • y being the numeric 'value'

    import pandas as pd
    import matplotlib.pyplot as plt
    
    df = pd.DataFrame({'value': [1771, 1644], 'gender': ['F', 'M']})
    
    plt.figure(figsize=(12, 6))
    bars = plt.bar(df.gender, df.value, width=0.1, bottom=None, align='center', data=None)
    for idx, (value, gender) in df.iterrows():
        plt.annotate(f'{value}\n', xy=(gender, value), ha='center', va='center')
    

    Plot Output

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