Python Matplotlib:将Y轴居中于0

我做了一个函数来描绘经济表现，但产出在y轴上往往是不平衡的

下图显示了问题所在。y值的范围使图表默认为最大/最小值作为y轴的范围

有没有办法强制图表将其自身居中于0，或者我是否需要在函数中导出最大和最小y值

函数如下所示。如果你想让我用值替换变量来重新调整图表lmk，那就有点麻烦了

def recession_comparison(key, variable, dimension):
    '''
    Creates the "scary chart"- proportional growth for a single area/industry. All recessions included in chart.

        Parameters: 
            key (str or int): area-fips or industry_code
            variable (str): determines what economic indicator will be used in the timeline. Must be one of ['month3_emplvl' (employment), 'avg_wkly_wage' (wages), 'qtrly_estabs_count'(firms)]
            dimension (str): dimension of data to chart.
            
        Returns: 
            fig (matplotlib plot)
    '''
    fig, ax = plt.subplots(figsize =(15, 10))
    if dimension == 'area':
        index = 'area_fips'
        title = 'Recession Comparison, ' + area_titles[key] + " (" + str(key) + ")" 
    elif dimension == 'industry':
        index = 'industry_code'
        title = 'Recession Comparison: ' + industry_titles[key] + " (" + str(key) + ")" 
    for recession in recessions_int.keys():
        if recession == 'full':
            break
        loadpath = filepath(variable = variable, dimension = dimension, charttype = 'proportional', recession = recession, filetype = 'json')
        df = pd.read_json(loadpath)
        df.set_index(index, inplace = True)
        ax.plot(df.loc[key][1:-1]*100, label = str(recession), linewidth = 1.5, alpha = 0.8)
    ax.axvline(x = 6, color = 'black', linewidth = 0.8, alpha = 0.5, ls = ':', label = 'Event Quarter')
    ax.axhline(y = 0, color = 'black', linewidth = 0.8, alpha = 0.5, ls = '--', label = 'Pre-Recession baseline')
    ax.set_xlabel('Quarters since start of recession')
    ax.set_ylabel('Growth: ' + var_display[variable])
    ax.set_title(title)
    ax.yaxis.set_major_formatter(mtick.PercentFormatter())
    plt.legend()
    plt.show()
    return fig

编辑：DapperDuck的完整代码解决方案：

def recession_comparison(key, variable, dimension):
    fig, ax = plt.subplots(figsize =(15, 10))
    if dimension == 'area':
        index = 'area_fips'
        title = 'Recession Comparison, ' + area_titles[key] + " (" + str(key) + ")" 
    elif dimension == 'industry':
        index = 'industry_code'
        title = 'Recession Comparison: ' + industry_titles[key] + " (" + str(key) + ")" 
    for recession in recessions_int.keys():
        if recession == 'full':
            break
        loadpath = filepath(variable = variable, dimension = dimension, charttype = 'proportional', recession = recession, filetype = 'json')
        df = pd.read_json(loadpath)
        df.set_index(index, inplace = True)
        ax.plot(df.loc[key][1:-1]*100, label = str(recession), linewidth = 1.5, alpha = 0.8)
    ax.axvline(x = 6, color = 'black', linewidth = 0.8, alpha = 0.5, ls = ':', label = 'Event Quarter')
    ax.axhline(y = 0, color = 'black', linewidth = 0.8, alpha = 0.5, ls = '--', label = 'Pre-Recession baseline')
    yabs_max = abs(max(ax.get_ylim(), key=abs))
    ax.set_ylim(ymin=-yabs_max, ymax=yabs_max)
    ax.set_xlabel('Quarters since start of recession')
    ax.set_ylabel('Growth: ' + var_display[variable])
    ax.set_title(title)
    ax.yaxis.set_major_formatter(mtick.PercentFormatter())
    plt.legend()
    plt.show()
    return fig

校正图像：

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在ax.axhline（y=0，颜色为“黑色”，线宽为0.8，alpha=0.5，ls='--'，标签为“衰退前基线”）之后添加以下代码。：

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请参见添加的图像。这并没有达到我们预期的效果。@CJH我更新了我的答案。试试看out@CJH更新后的解决方案有效吗？我只是想澄清一下，您是希望y轴以x轴“0”为中心，还是希望x轴以y轴“0”为中心，或者两者兼而有之，现在我明白您的意思了。我将编辑我的答案以备将来参考。这个问题对。。。看起来不像。我不想移动脊椎或刻度，我希望水平0线始终位于图表的中心。

yabs_max = abs(max(ax.get_ylim(), key=abs))
ax.set_ylim(ymin=-yabs_max, ymax=yabs_max)