如何强制在matplotlib上设置x刻度，或设置没有年份的日期时间类型 [英] How to force set x ticks on matplotlib, or set datetime type with no year

问题描述

因此，我有一个函数将获取一个pandas数据框并对其进行绘制，并显示一些错误度量，并且我也有一个函数将获取一个带有日期时间类型索引的pandas数据框，并获取每日平均值数据框中的值.问题是，当我尝试绘制每日平均值时，使用matplotlib看起来确实很糟糕，因为它将每日绘制为x轴上的单独刻度.我将所有这些代码保存在名为Hydrostats的程序包中，每日平均功能的github存储库源代码为此处，绘图功能的源代码为

So I have a function that will take a pandas dataframe and plot it, along with displaying some error metrics, and I also have a function that will take a pandas dataframe with a datetime type index, and take the daily average of the values in the dataframe. The problem is, when I try to plot the daily average, it looks really bad with matplotlib because it plots everyday as a seperate tick on the x axis. I have all this code in a package called Hydrostats, the github reposity source code for the daily average function is here, and the source code for the plotting function is here. The plot for a linear time series is is below. The Daily Average plot is shown below

如您所见，您看不到任何x轴刻度，因为它们都被挤压在一起了.

As you can see, you can't see any of the x axis ticks because they are all so squished together.

推荐答案

您可以通过 ax.set_xticklabels() .

You can set the ticks used for the x axis via ax.set_xticks() and labels via ax.set_xticklabels().

例如，您可以为该方法提供要使用的日期列表，例如当前pd.DataFrame索引(df.index[::20])的每20个值，然后按如下所示设置日期字符串的格式.

For instance you could just provide that method with a list of dates to use, such as every 20th value of the current pd.DataFrame index (df.index[::20]) and then set the formatting of the date string as below.

# Get the current axis
ax = plt.gca()

# Only label every 20th value
ticks_to_use = df.index[::20]

# Set format of labels (note year not excluded as requested)
labels = [ i.strftime("%-H:%M") for i in ticks_to_use ]

# Now set the ticks and labels
ax.set_xticks(ticks_to_use)
ax.set_xticklabels(labels)

注释

如果标签仍然重叠，您还可以通过传递旋转参数(例如ax.set_xticklabels(labels, rotation=45))来旋转标签.

If labels still overlap, you could also rotate the them by passing the rotatation argument (e.g. ax.set_xticklabels(labels, rotation=45)).

此处提供了有关时间字符串格式的有用参考: http://strftime.org .

There is a useful reference for time string formats here: http://strftime.org.

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