为多个子图设置具有固定指数和有效数字的科学计数法 [英] Set scientific notation with fixed exponent and significant digits for multiple subplots

问题描述

我正在尝试将轴固定为两组不同数据的科学计数法，其中一组是[1-9] x1e-3，另一组是[1-9] x1e-4.我想将两个轴都设置为10 ^ -4，并在小数点后添加一位数字(例如％.1e).这是我尝试使用的一个简单版本:我希望轴上的数字至少为1，并且我希望两个幂都相同.

I am trying to fix the axes to scientific notation of two different sets of data where one is [1-9]x1e-3 and the other is [1-9]x1e-4. I would like to set both axes to be 10^-4 and have the one digits after decimal (e.g. %.1e). Here is a simple version that I have tried to play around with: I would like the numbers on the axes to be at least 1 and I want both powers to be the same.

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(1,9,9)
y1 = x*10**(-4)
y2 = x*10**(-3)

fig, ax = plt.subplots(2,1,sharex=True)

ax[0].plot(x,y1)
ax[0].ticklabel_format(axis='y', style='sci', scilimits=(-4,-4))
ax[0].yaxis.major.formatter._useMathText = True
ax[1].plot(x,y2)
ax[1].ticklabel_format(axis='y', style='sci', scilimits=(-4,-4))
ax[1].yaxis.major.formatter._useMathText = True

plt.show()

推荐答案

您可以将matplotlib.ticker.ScalarFormatter子类化，并将orderOfMagnitude属性固定为所需的数字(在本例中为-4).
以相同的方式，您可以固定要使用的格式.

You can subclass matplotlib.ticker.ScalarFormatter and fix the orderOfMagnitude attribute to the number you like (in this case -4).
In the same way you can fix the format to be used.

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker

class OOMFormatter(matplotlib.ticker.ScalarFormatter):
    def __init__(self, order=0, fformat="%1.1f", offset=True, mathText=True):
        self.oom = order
        self.fformat = fformat
        matplotlib.ticker.ScalarFormatter.__init__(self,useOffset=offset,useMathText=mathText)
    def _set_order_of_magnitude(self):
        self.orderOfMagnitude = self.oom
    def _set_format(self, vmin=None, vmax=None):
        self.format = self.fformat
        if self._useMathText:
            self.format = r'$\mathdefault{%s}$' % self.format


x = np.linspace(1,9,9)
y1 = x*10**(-4)
y2 = x*10**(-3)

fig, ax = plt.subplots(2,1,sharex=True)

ax[0].plot(x,y1)
ax[1].plot(x,y2)

for axe in ax:
    axe.yaxis.set_major_formatter(OOMFormatter(-4, "%1.1f"))
    axe.ticklabel_format(axis='y', style='sci', scilimits=(-4,-4))

plt.show()

虽然乍看之下似乎很复杂，但实际上唯一要做的就是覆盖私有方法_set_orderOfMagnitude和_set_format，从而防止它们在我们不希望的后台执行某些复杂的工作.因为最后，我们所需要做的就是，独立于内部发生的事情，self.orderOfMagnitude始终为-4，而self.format始终为"%1.1f".

While this may seem complicated at first sight the only thing it really does is overwrite the private methods _set_orderOfMagnitude and _set_format and thereby prevent them from doing some sophisticated stuff in the background that we don't want. Because in the end, all we need is that, independent of what happens internally, self.orderOfMagnitude is always -4 and self.format is always "%1.1f".

注意:在matplotlib中< 3.1所需的类看起来像

Note: In matplotlib < 3.1 the class needed to look like

class OOMFormatter(matplotlib.ticker.ScalarFormatter):
        def __init__(self, order=0, fformat="%1.1f", offset=True, mathText=True):
            self.oom = order
            self.fformat = fformat
            matplotlib.ticker.ScalarFormatter.__init__(self,useOffset=offset,useMathText=mathText)
        def _set_orderOfMagnitude(self, nothing=None):
            self.orderOfMagnitude = self.oom
        def _set_format(self, vmin=None, vmax=None):
            self.format = self.fformat
            if self._useMathText:
                self.format = '$%s$' % matplotlib.ticker._mathdefault(self.format)

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