221 lines
5.9 KiB
Markdown
221 lines
5.9 KiB
Markdown
|
# NumPy Arccos-完全指南
|
|||
|
|
|
|||
|
|
> 原文:# t0]https://www . aspython . com/python-modules/num py/numpy-arccos
|
|||
|
|
|
|||
|
|
读者你好！在本教程中，我们将理解 **NumPy arccos** 函数以及大量的例子。我们还将绘制`arccos`函数的曲线。那么，我们开始吧。
|
|||
|
|
|
|||
|
|
***亦读:[【NumPy Arctan-完全指南】](https://www.askpython.com/python-modules/numpy/numpy-arctan)***
|
|||
|
|
|
|||
|
|
## Arccos 函数-快速概述
|
|||
|
|
|
|||
|
|
* **arccos** 是**余弦**函数的逆的表示。
|
|||
|
|
* arccos 函数接受范围为 **[-1，1]** 的输入，并产生范围为 **[0，pi]** 的输出。
|
|||
|
|
|
|||
|
|
## 什么是 NumPy Arccos？
|
|||
|
|
|
|||
|
|
NumPy Arccos 是 NumPy 库提供的三角函数之一。NumPy Arccos 可以将**实数**和**复数**作为输入。
|
|||
|
|
|
|||
|
|
我们可以以`**numpy.arccos**`的身份访问 NumPy Arccos 函数。
|
|||
|
|
|
|||
|
|
## NumPy arccos 的语法
|
|||
|
|
|
|||
|
|
**语法:** `**numpy.arccos(input)**`其中输入可以是单个数字，也可以是数字的 NumPy 数组。
|
|||
|
|
|
|||
|
|
让我们写一些代码。
|
|||
|
|
|
|||
|
|
## 单个数的 NumPy arccos
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
import math
|
|||
|
|
|
|||
|
|
print("Printing the Cosine inverse values in radians\n")
|
|||
|
|
|
|||
|
|
print("Cos inverse of 0 is :",np.arccos(0))
|
|||
|
|
|
|||
|
|
print("Cos inverse of 0.5 is :",np.arccos(0.5))
|
|||
|
|
|
|||
|
|
print("Cos inverse of 1/sqrt(2) is :",np.arccos(1/math.sqrt(2)))
|
|||
|
|
|
|||
|
|
print("Cos inverse of 1 is :",np.arccos(1))
|
|||
|
|
|
|||
|
|
print("Cos inverse of -1 is :",np.arccos(-1))
|
|||
|
|
|
|||
|
|
print("\n")
|
|||
|
|
|
|||
|
|
print("Cosine inverse values in degrees\n")
|
|||
|
|
|
|||
|
|
print("Cos inverse of 1/sqrt(2) is :",np.degrees(np.arccos(1/math.sqrt(2))))
|
|||
|
|
|
|||
|
|
print("Cos inverse of -1 is :",np.degrees(np.arccos(-1)))
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**输出**
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
Printing the Cosine inverse values in radians
|
|||
|
|
|
|||
|
|
Cos inverse of 0 is : 1.5707963267948966
|
|||
|
|
Cos inverse of 0.5 is : 1.0471975511965979
|
|||
|
|
Cos inverse of 1/sqrt(2) is : 0.7853981633974484
|
|||
|
|
Cos inverse of 1 is : 0.0
|
|||
|
|
Cos inverse of -1 is : 3.141592653589793
|
|||
|
|
|
|||
|
|
Cosine inverse values in degrees
|
|||
|
|
|
|||
|
|
Cos inverse of 1/sqrt(2) is : 45.00000000000001
|
|||
|
|
Cos inverse of -1 is : 180.0
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
让我们以 0 的 cos 逆为例，它等于 90 度。因为 90 度的余弦是 0，所以 0 的反余弦是 90 度。这是理解反三角函数如何计算结果的一种有趣方式。
|
|||
|
|
|
|||
|
|
任务:尝试将 NumPy Arccos 函数与其他输入一起使用，并观察输出。
|
|||
|
|
|
|||
|
|
### 复数的 NumPy arccos
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
print("Cosine inverse of 1+5j is: ",np.arccos(1+5j))
|
|||
|
|
|
|||
|
|
print("Cosine inverse of 2+3j is: ",np.arccos(2+3j))
|
|||
|
|
|
|||
|
|
print("Cosine inverse of 0.5+0.5j is: ",np.arccos(0.5+0.5j))
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**输出**
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
Cosine inverse of 1+5j is: (1.3770031902399644-2.3309746530493123j)
|
|||
|
|
Cosine inverse of 2+3j is: (1.0001435424737972-1.9833870299165355j)
|
|||
|
|
Cosine inverse of 0.5+0.5j is: (1.118517879643706-0.5306375309525179j)
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### 无效数字的 NumPy arccos
|
|||
|
|
|
|||
|
|
如果将无效输入作为参数传递给 arccos 函数，则输出将为 **`nan`** 。
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
print("Cosine inverse of -3 is :",np.arccos(5))
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
输出
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
Cosine inverse of -3 is : nan
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**注意:**超出范围[-1，1]的每个数字都被视为`arccos`函数的无效输入。
|
|||
|
|
|
|||
|
|
## 多个数字上的 NumPy Arccos
|
|||
|
|
|
|||
|
|
arccos 函数也将 NumPy 数字数组作为参数。
|
|||
|
|
|
|||
|
|
### 将 NumPy 数组与 Arccos 相结合
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
a = np.array((-1 , 0 , 0.5 , 0.3 , 1))
|
|||
|
|
|
|||
|
|
print("Cosine Inverse Values in radians :\n",np.arccos(a))
|
|||
|
|
|
|||
|
|
print("Cosine Inverse Values in degrees :\n",np.degrees(np.arccos(a)))
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**输出**
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
Cosine Inverse Values in radians :
|
|||
|
|
[3.14159265 1.57079633 1.04719755 1.26610367 0\. ]
|
|||
|
|
Cosine Inverse Values in degrees :
|
|||
|
|
[180\. 90\. 60\. 72.54239688 0\. ]
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### 均匀间隔的数字阵列
|
|||
|
|
|
|||
|
|
在这个例子中，我们将使用`**numpy.linspace**`创建一个由 20 个等距值组成的 NumPy 数组。
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
a = np.linspace(-1 , 1 , 20)
|
|||
|
|
|
|||
|
|
print("Cosine Inverse Values in radians: ",np.arccos(a))
|
|||
|
|
|
|||
|
|
print("Cosine Inverse Values in degrees: ",np.degrees(np.arccos(a)))
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**输出**
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
Cosine Inverse Values in radians: [3.14159265 2.67863793 2.48074736 2.32431694 2.18823343 2.06426572
|
|||
|
|
1.94810636 1.83709034 1.72935461 1.62345224 1.51814042 1.41223805
|
|||
|
|
1.30450231 1.19348629 1.07732693 0.95335922 0.81727571 0.6608453
|
|||
|
|
0.46295473 0\. ]
|
|||
|
|
Cosine Inverse Values in degrees: [180\. 153.47464798 142.13635364 133.17355111 125.37654015
|
|||
|
|
118.27371363 111.61827242 105.25752329 99.08472029 93.01696131
|
|||
|
|
86.98303869 80.91527971 74.74247671 68.38172758 61.72628637
|
|||
|
|
54.62345985 46.82644889 37.86364636 26.52535202 0\. ]
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 可视化 Arccos 函数
|
|||
|
|
|
|||
|
|
```py
|
|||
|
|
import numpy as np
|
|||
|
|
|
|||
|
|
# Importing the Matplotlib Library
|
|||
|
|
import matplotlib.pyplot as plt
|
|||
|
|
|
|||
|
|
# Creating a NumPy Array of 30 evenly-spaced elements
|
|||
|
|
a = np.linspace(-1,1,30)
|
|||
|
|
|
|||
|
|
# Storing the computed arccos values in a NumPy Array
|
|||
|
|
b = np.arccos(a)
|
|||
|
|
plt.plot(a, b, color = "green", marker = "o")
|
|||
|
|
plt.title("numpy.arccos()")
|
|||
|
|
plt.xlabel("X")
|
|||
|
|
plt.ylabel("Y")
|
|||
|
|
plt.show()
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
**输出**
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
**Arccos Plot**
|
|||
|
|
|
|||
|
|
**注:**在图中，Y 轴(纵轴)上的数值是`**arccos**`函数的输出，单位为**弧度**。
|
|||
|
|
|
|||
|
|
`**plt.plot()**`该函数用于绘制带三个参数的 **arccos** 函数。
|
|||
|
|
|
|||
|
|
* 第**个**参数是数字的 **NumPy 数组**(在第 3 行创建)，绘制在 X 轴(水平轴)上。
|
|||
|
|
* 第二个参数**是`**arccos**`函数的输出，绘制在 Y 轴(垂直轴)上。**
|
|||
|
|
* 第三个参数是绘图的颜色。
|
|||
|
|
* **第四个**参数是标记值，用指定的标记强调每个点。有不同类型的标记可用于表示曲线上的点。
|
|||
|
|
|
|||
|
|
好了，你已经使用 Matplotlib 库绘制了`**arccos**`曲线。
|
|||
|
|
|
|||
|
|
## 摘要
|
|||
|
|
|
|||
|
|
所以，我们学习了 NumPy 库的`**arccos**`函数。在下一个教程中，我们将介绍 [**`arctan`** 功能](https://www.askpython.com/python-modules/numpy/numpy-arctan)。直到那时继续学习，继续编码:)。
|
|||
|
|
|
|||
|
|
## 参考
|
|||
|
|
|
|||
|
|
[num py documentation–num py arccos](https://numpy.org/doc/stable/reference/generated/numpy.arccos.html)
|
|||
|
|
|
|||
|
|
[Matplotlib–开始使用](https://matplotlib.org/stable/users/getting_started/)
|