没有 NaN 值空间的 Pandas 绘图条

Posted 2023-03-11

【中文标题】没有 NaN 值空间的 Pandas 绘图条

【英文标题】：Pandas plot bar without NaN values spaces

【发布时间】：2019-04-23 06:03:40

【问题描述】：

我有一个包含 NaN 值的 pandas DataFrame。我想用 x axys 中的索引制作一个条形图，每列都有一个条形图，按索引分组。我想只绘制具有实际值的条形图。

就我而言，从这个例子：

df = pandas.DataFrame('foo':[1,None,None], 'bar':[None,2,0.5], 'col': [1,1.5,None], index=["A","B","C"])
df.plot.bar()
plt.show()

我可以制作这个情节：

我想要删除为 NaN 列留下的空格。所以要压缩条形并将组居中在 x 刻度上方。

【问题讨论】：

无法直接使用 pandas。您可以查看how matplotlib grouped barcharts 的制作并根据您的情况进行调整。

这能回答你的问题吗？ How do you remove spaces between bars in bar charts for where plotted values are zero?

【参考方案1】：

您可以通过遍历数据框的每一行来执行以下代码的操作 并检查每一列的 NaN。

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame(
    "foo": [1, None, None], "bar": [None, 2, 0.5], "col": [1, 1.5, None],
    index=["A", "B", "C"],
)


# define the colors for each column
colors = "foo": "blue", "bar": "orange", "col": "green"

fig = plt.figure(figsize=(10, 6))
ax = plt.gca()

# width of bars
width = 1

# create emptly lists for x tick positions and names
x_ticks, x_ticks_pos = [], []

# counter for helping with x tick positions
count = 0

# reset the index
# so that we can iterate through the numbers.
# this will help us to get the x tick positions
df = df.reset_index()
# go through each row of the dataframe
for idx, row in df.iterrows():
    # this will be the first bar position for this row
    count += idx

    # this will be the start of the first bar for this row
    start_idx = count - width / 2
    # this will be the end of the last bar for this row
    end_idx = start_idx
    # for each column in the wanted columns,
    # if the row is not null,
    # add the bar to the plot
    # also update the end position of the bars for this row
    for column in df.drop(["index"], axis=1).columns:
        if row[column] == row[column]:
            plt.bar(count, row[column], color=colors[column], width=width, label=column)
            count += 1
            end_idx += width
    # this checks if the row had any not NULL value in the desired columns
    # in other words, it checks if there was any bar for this row
    # if yes, add the center of all the row's bars and the row's name (A,B,C) to the respective lists
    if end_idx != start_idx:
        x_ticks_pos.append((end_idx + start_idx) / 2)
        x_ticks.append(row["index"])

# now set the x_ticks
plt.xticks(x_ticks_pos, x_ticks)

# also plot the legends
# and make sure to not display duplicate labels
# the below code is taken from:
# https://***.com/questions/13588920/stop-matplotlib-repeating-labels-in-legend
handles, labels = plt.gca().get_legend_handles_labels()
by_label = dict(zip(labels, handles))
plt.legend(by_label.values(), by_label.keys())
plt.show()

结果：