Seaborn / Matplotlib日期轴条形图-小刻度线格式 [英] Seaborn/Matplotlib Date Axis barplot minor-major tick formatting

问题描述

我正在建立一个Seaborn的地块。 x轴是日期，y轴是整数。

我想格式化日期的主要/次要刻度。我希望星期一的刻度线为粗体，并且使用不同的颜色（即主要刻度线），而本周的其余时间则不那么粗体。

我还没有能够在X轴上获得主要和次要的刻度线格式，从而可以与Seaborn条形图一起使用。我很困惑，因此转向这里寻求帮助。

我从回答这个问题的stackoverflow示例开始：

I'm building a Seaborn barplot. The x-axis are dates, and the y-axis are integers.

I'd like to format major/minor ticks for the dates. I'd like Mondays' ticks to be bold and a different color (ie, "major ticks"), with the rest of the week less bold.

I have not been able to get major and minor tick formatting on the x-axis to work with Seaborn barplots. I'm stumped, and thus turning here for help.

I'm starting with the stackoverflow example that answered this question: Pandas timeseries plot setting x-axis major and minor ticks and labels

If I do a simple modification it to use a Seaborn barplot and I lose my X-axis ticks:

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as dates

import seaborn as sns

idx = pd.date_range('2011-05-01', '2011-07-01')
s = pd.Series(np.random.randn(len(idx)), index=idx)

###########################################
## Swap out these two lines of code:
#fig, ax = plt.subplots()
#ax.plot_date(idx.to_pydatetime(), s, 'v-')

## with this one
ax = sns.barplot(idx.to_pydatetime(), s)
###########################################

ax.xaxis.set_minor_locator(dates.WeekdayLocator(byweekday=(1),
                                                interval=1))
ax.xaxis.set_minor_formatter(dates.DateFormatter('%d\n%a'))
ax.xaxis.grid(True, which="minor")
ax.yaxis.grid()
ax.xaxis.set_major_locator(dates.MonthLocator())
ax.xaxis.set_major_formatter(dates.DateFormatter('\n\n\n%b\n%Y'))
plt.tight_layout()

## save the result to a png instead of plotting to screen:
myFigure = plt.gcf()
myFigure.autofmt_xdate()
myFigure.set_size_inches(11,3.8)

plt.title('Example Chart', loc='center')

plt.savefig('/tmp/chartexample.png', format='png', bbox_inches='tight')

I've tried a variety of approaches but something in Seaborn seems to be overriding or undoing any attempts at major and minor axis formatting that I've managed to cook up yet beyond some simple styling for all ticks when I use set_xticklabels().

I can sort of get formatting on just the major ticks by using MultipleLocator(), but I can't get any formatting on the minor ticks.

I've also experimented with myFigure.autofmt_xdate() to see if it would help, but it doesn't seem to like mixed major & minor ticks on the same axis either.

解决方案

I came across this while trying to solve the same problem. Based on the useful pointer from @mwaskom (that categorical plots like boxplots lose their structure and just become date-named categories) and ended up doing the location and formatting in Python as so:

from datetime import datetime
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as dates
import seaborn as sns

idx = pd.date_range('2011-05-01', '2011-07-01')
s = pd.Series(np.random.randn(len(idx)), index=idx)

fig, ax = plt.subplots(figsize = (12,6))
ax = sns.barplot(idx.to_pydatetime(), s, ax = ax)

major_ticks = []
major_tick_labels = []
minor_ticks = []
minor_tick_labels = []

for loc, label in zip(ax.get_xticks(), ax.get_xticklabels()):
  when = datetime.strptime(label.get_text(), '%Y-%m-%d %H:%M:%S')
  if when.day == 1:
    major_ticks.append(loc)
    major_tick_labels.append(when.strftime("\n\n\n%b\n%Y"))
  else:
    minor_ticks.append(loc)
    if when.weekday() == 0:
      minor_tick_labels.append(when.strftime("%d\n%a"))
    else:
      minor_tick_labels.append(when.strftime("%d"))

ax.set_xticks(major_ticks)
ax.set_xticklabels(major_tick_labels)
ax.set_xticks(minor_ticks, minor=True)
ax.set_xticklabels(minor_tick_labels, minor=True)

Of course, you don't have to set the ticks based on parsing the labels which were installed from the data, if it's easier to start with the source data and just keep the indices aligned, but I prefer to have a single source of truth.

You can also mess with font weight, rotation, etc, on individual labels by getting the Text objects for the relevant label and calling set_ methods on it.

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