如何修改Matplotlib分组柱状图X轴标签并优化分组间距？

我编写了一个Python函数来生成分组柱状图，目前图表可正常运行，但X轴会针对data_list中的每个子列表重复显示1,2,3,4,5,6,7,8,9,10。我希望改为每个分组仅显示一次该标签，并且将10组柱状图彼此分隔开，使其更清晰易读。

原代码如下：

import matplotlib.pyplot as plt

def plot_graph(list, title_str):

    x_plot = []
    y_plot  = []
    legend_labels = ['a', 'b', 'c', 'd', 'e', 'f']
    x_labels = [1,2,3,4,5,6,7,8,9,10]
    x_labels_text = ['red', 'blue', 'green', 'purple', 'olive', 'brown']
    x_colors = ['tab:red', 'tab:blue', 'tab:green', 'tab:purple', 'tab:olive', 'tab:brown']
    fig, ax = plt.subplots()
    ax.set_xlabel('\nFault Type', fontsize=15)
    ax.set_ylabel('Number of Errors (%)', fontsize=15)
    ax.set_title('Total Number of Errors (%)', fontsize=15)

    for i in range(len(list)):
        for j in range(len(list[i])):
            x_plot.append(x_labels[i])
            y_plot.append(list[i][j])

    ax.bar(range(len(x_plot)), y_plot, label=legend_labels, color=x_colors, width=0.5)
    ax.set_xticks(range(len(x_plot)), x_plot)
    ax.set_ylim(ymax=100)

    #ax.legend(['a', 'b', 'c', 'd', 'e', 'f'])
    patches, _ = ax.get_legend_handles_labels()
    labels = [*'abcdef']
    ax.legend(*patches, labels, loc='best')

    fig.tight_layout()

    plt.setp(ax.get_xticklabels(), fontsize=10)
    plt.savefig("C:/CoolTermWin64Bit/CoolTermWin64Bit/uart_data/Gathered Data/Code Generated Data Files/" + title_str + ".pdf")


data_list = [  [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60],
               [10, 20, 30, 40, 50, 60]  ]

plot_graph(data_list, "data grouped bar graph")

原图表效果：

通过调整柱子位置计算、X轴刻度设置以及分组间距，可实现需求。修改后的代码如下：

import matplotlib.pyplot as plt

def plot_graph(data_list, title_str):
    legend_labels = ['a', 'b', 'c', 'd', 'e', 'f']
    x_group_labels = [1,2,3,4,5,6,7,8,9,10]  # 每个分组的唯一标签
    x_colors = ['tab:red', 'tab:blue', 'tab:green', 'tab:purple', 'tab:olive', 'tab:brown']
    fig, ax = plt.subplots(figsize=(12, 6))  # 调整画布适配分组显示
    ax.set_xlabel('\nFault Type', fontsize=15)
    ax.set_ylabel('Number of Errors (%)', fontsize=15)
    ax.set_title('Total Number of Errors (%)', fontsize=15)

    num_groups = len(data_list)  # 分组总数：10
    num_bars_per_group = len(data_list[0])  # 每组内柱子数量：6
    bar_width = 0.14  # 缩小单柱宽度，预留分组间距
    group_spacing = 0.2  # 分组之间的间隔

    # 遍历每个分组，计算每组内柱子的X坐标
    for group_idx in range(num_groups):
        # 当前分组的基准X位置
        base_x = group_idx * (num_bars_per_group * bar_width + group_spacing)
        # 绘制组内每一根柱子
        for bar_idx in range(num_bars_per_group):
            x_pos = base_x + bar_idx * bar_width
            # 仅在第一个分组添加图例标签，避免重复
            ax.bar(x_pos, data_list[group_idx][bar_idx], width=bar_width, 
                   color=x_colors[bar_idx], label=legend_labels[bar_idx] if group_idx == 0 else "")

    # 设置X轴刻度：每个分组的中间位置对应一个标签
    tick_positions = [i * (num_bars_per_group * bar_width + group_spacing) + (num_bars_per_group * bar_width)/2 for i in range(num_groups)]
    ax.set_xticks(tick_positions, x_group_labels, fontsize=10)
    ax.set_ylim(ymax=100)

    ax.legend(loc='best')
    fig.tight_layout()
    plt.savefig(f"C:/CoolTermWin64Bit/CoolTermWin64Bit/uart_data/Gathered Data/Code Generated Data Files/{title_str}.pdf")
    plt.show()

data_list = [
    [10, 20, 30, 40, 50, 60], [10, 20, 30, 40, 50, 60],
    [10, 20, 30, 40, 50, 60], [10, 20, 30, 40, 50, 60],
    [10, 20, 30, 40, 50, 60], [10, 20, 30, 40, 50, 60],
    [10, 20, 30, 40, 50, 60], [10, 20, 30, 40, 50, 60],
    [10, 20, 30, 40, 50, 60], [10, 20, 30, 40, 50, 60]
]

plot_graph(data_list, "data grouped bar graph")

关键改动说明 #

• 分组位置规划：为每个分组设置独立的基准X坐标，组内柱子按宽度依次排列，通过group_spacing实现组间分隔。
• X轴刻度优化：将刻度点放在每个分组的中间位置，仅显示一次分组标签，避免重复。
• 图例简化：仅在第一个分组生成图例标签，防止图例重复出现。
• 画布适配：调整画布宽度，配合缩小的柱子宽度，让分组显示更舒展清晰。

内容的提问来源于stack exchange，提问作者David777