Question

我想根据 >pi 的比例写入轴的弧度单位:类似的东西

$frac{pi}{4}$, $frac{pi}{2}$, ...

以

0.785, 1.5707 ...

Is there any standard way? As an example, what should I add to the following code?

from pylab import *

x=arange(-10.0,10.0,0.1)
y= arctan(x)

plot(x,y, b. )
show()

我找到了这个例子"http://matplotlib.sourceforge.net/examples/units/radioan_demo.html>,但因为我没有基本单位模块,所以它行不通。

谢谢!

Answer 1

硬硬以分数编码它们, 或者接受浮动数字

import matplotlib.pyplot as plt
import numpy as np

x=np.arange(-10.0,10.0,0.1)
y=np.arctan(x)

fig = plt.figure()
ax  = fig.add_subplot(111)

ax.plot(x,y, b. )

y_pi   = y/np.pi
unit   = 0.25
y_tick = np.arange(-0.5, 0.5+unit, unit)

y_label = [r"$-frac{pi}{2}$", r"$-frac{pi}{4}$", r"$0$", r"$+frac{pi}{4}$",   r"$+frac{pi}{2}$"]
ax.set_yticks(y_tick*np.pi)
ax.set_yticklabels(y_label, fontsize=20)

y_label2 = [r"$" + format(r, ".2g")+ r"pi$" for r in y_tick]
ax2 = ax.twinx()
ax2.set_yticks(y_tick*np.pi)
ax2.set_yticklabels(y_label2, fontsize=20)

plt.show()

结果为

""https://i.sstatic.net/f2PIf.png" alt="此处的内置图像描述"/ >

Answer 2

我写了一个小函数, 给了您一个标签列表 :

import numpy as np
from fractions import Fraction

def create_pi_labels(a, b, step):

    max_denominator = int(1/step)
    # i added this line and the .limit_denominator to solve an 
    # issue with floating point precision
    # because of floataing point precision Fraction(1/3) would be 
    # Fraction(6004799503160661, 18014398509481984)

    values = np.arange(a, b+step/10, step)
    fracs = [Fraction(x).limit_denominator(max_denominator) for x in values]
    ticks = values*np.pi

    labels = []

    for frac in fracs:
        if frac.numerator==0:
            labels.append(r"$0$")
        elif frac.numerator<0:
            if frac.denominator==1 and abs(frac.numerator)==1:
                labels.append(r"$-pi$")
            elif frac.denominator==1:
                labels.append(r"$-{}pi$".format(abs(frac.numerator)))
            else:
                labels.append(r"$-frac{{{}}}{{{}}} pi$".format(abs(frac.numerator), frac.denominator))
        else:
            if frac.denominator==1 and frac.numerator==1:
                labels.append(r"$pi$")
            elif frac.denominator==1:
                labels.append(r"${}pi$".format(frac.numerator))
            else:
                labels.append(r"$frac{{{}}}{{{}}} pi$".format(frac.numerator, frac.denominator))

    return ticks, labels

https://github.com/maxNoe/python-plotting/blob/master/source/source/cource/create_pi_lables.py" rel=“no follow'>https://github.com/maxnoe/python-plotting/blob/master/sourc/sourc/sourc/sourc/cation_pi_lables.p

Answer 3

您可以下载基本的_units.py file :

之后,它应该这样工作:

from pylab import *
from basic_units import radians

x = arange(-10.0,10.0,0.1)
y = map(lambda y: y*radians,arctan(x))
x = map(lambda x: x*radians,x)

plot(x,y, b. ,xunits=radians,yunits=radians)
show()

或者您也可以在基本单位中执行 orctan 函数, 以它们执行 cos 函数的方式执行 irctan 函数。

Answer 4

我创建了一个 < a href=> "https://pypi.org/project/matplot-fmt-pi/" rel="notfollown noreferrer" >PyPi软件包 ,可以格式化和在 pi 分数的倍数上放置 tits。

"""Show an example of using MultiplePi on the y-axis."""
import matplotlib.pyplot as plt
import numpy as np

from matplot_fmt_pi import MultiplePi

x = np.arange(-10.0, 10.0, 0.1)
y = np.arctan(x)

fig = plt.figure()
ax = fig.add_subplot(111)

ax.set_title("MultiplePi formatting")
ax.plot(x, y,  b. )

y_pi = y / np.pi
unit = 0.25
y_tick = np.arange(-0.5, 0.5 + unit, unit)

# New way
manager = MultiplePi(4)
ax.yaxis.set_major_locator(manager.locator())
ax.yaxis.set_major_formatter(manager.formatter())

# Other way
y_label2 = [r"$" + format(r, ".2g") + r"pi$" for r in y_tick]
ax2 = ax.twinx()
ax2.set_yticks(y_tick * np.pi)
ax2.set_yticklabels(y_label2)

plt.savefig("./pi_y_axis.png", dpi=120)

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