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323 lines
2.9 KiB
Markdown
323 lines
2.9 KiB
Markdown
# 一般函数
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In [1]:
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```py
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import numpy as np
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```
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## 三角函数
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```py
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sin(x)
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cos(x)
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tan(x)
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sinh(x)
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conh(x)
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tanh(x)
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arccos(x)
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arctan(x)
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arcsin(x)
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arccosh(x)
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arctanh(x)
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arcsinh(x)
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arctan2(x,y)
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```
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`arctan2(x,y)` 返回 `arctan(x/y)` 。
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## 向量操作
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```py
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dot(x,y)
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inner(x,y)
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cross(x,y)
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vdot(x,y)
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outer(x,y)
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kron(x,y)
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tensordot(x,y[,axis])
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```
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## 其他操作
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```py
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exp(x)
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log(x)
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log10(x)
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sqrt(x)
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absolute(x)
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conjugate(x)
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negative(x)
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ceil(x)
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floor(x)
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fabs(x)
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hypot(x)
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fmod(x)
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maximum(x,y)
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minimum(x,y)
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```
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`hypot` 返回对应点 `(x,y)` 到原点的距离。
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In [2]:
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```py
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x = np.array([1,2,3])
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y = np.array([4,5,6])
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np.hypot(x,y)
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```
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Out[2]:
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```py
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array([ 4.12310563, 5.38516481, 6.70820393])
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```
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## 类型处理
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```py
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iscomplexobj
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iscomplex
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isrealobj
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isreal
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imag
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real
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real_if_close
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isscalar
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isneginf
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isposinf
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isinf
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isfinite
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isnan
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nan_to_num
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common_type
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typename
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```
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正无穷：
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In [3]:
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```py
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np.inf
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```
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Out[3]:
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```py
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inf
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```
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负无穷：
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In [4]:
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```py
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-np.inf
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```
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Out[4]:
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```py
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-inf
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```
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非法值（Not a number）：
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In [5]:
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```py
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np.nan
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```
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Out[5]:
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```py
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nan
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```
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检查是否为无穷：
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In [6]:
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```py
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np.isinf(1.0)
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```
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Out[6]:
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```py
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False
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```
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In [7]:
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```py
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np.isinf(np.inf)
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```
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Out[7]:
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```py
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True
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```
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In [8]:
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```py
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np.isinf(-np.inf)
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```
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Out[8]:
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```py
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True
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```
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非法值：
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In [9]:
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```py
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np.array([0]) / 0.0
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```
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```py
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c:\Miniconda\lib\site-packages\IPython\kernel\__main__.py:1: RuntimeWarning: invalid value encountered in divide
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if __name__ == '__main__':
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```
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Out[9]:
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```py
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array([ nan])
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```
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这并不会报错，而是返回一个非法值。
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只有 `0/0` 会得到 `nan`，非0值除以0会得到无穷：
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In [10]:
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```py
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a = np.arange(5.0)
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b = a / 0.0
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b
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```
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```py
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c:\Miniconda\lib\site-packages\IPython\kernel\__main__.py:2: RuntimeWarning: divide by zero encountered in divide
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from IPython.kernel.zmq import kernelapp as app
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c:\Miniconda\lib\site-packages\IPython\kernel\__main__.py:2: RuntimeWarning: invalid value encountered in divide
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from IPython.kernel.zmq import kernelapp as app
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```
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Out[10]:
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```py
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array([ nan, inf, inf, inf, inf])
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```
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`nan` 与任何数进行比较都是 `False`：
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In [11]:
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```py
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b == np.nan
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```
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Out[11]:
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```py
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array([False, False, False, False, False], dtype=bool)
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```
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想要找出 `nan` 值需要使用 `isnan`：
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In [12]:
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```py
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np.isnan(b)
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```
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Out[12]:
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```py
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array([ True, False, False, False, False], dtype=bool)
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```
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## 修改形状
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```py
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atleast_1d
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atleast_2d
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atleast_3d
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expand_dims
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apply_over_axes
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apply_along_axis
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hstack
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vstack
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dstack
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column_stack
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hsplit
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vsplit
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dsplit
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split
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squeeze
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```
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## 其他有用函数
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```py
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fix
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mod
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amax
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amin
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ptp
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sum
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cumsum
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prod
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cumprod
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diff
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angle
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unwrap
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sort_complex
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trim_zeros
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fliplr
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flipud
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rot90
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diag
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eye
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select
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extract
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insert
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roots
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poly
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any
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all
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disp
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unique
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nansum
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nanmax
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nanargmax
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nanargmin
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nanmin
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```
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`nan` 开头的函数会进行相应的操作，但是忽略 `nan` 值。 |