【转】np.linspace()、np.logspace()、np.arange()

转自：https://blog.csdn.net/ui_shero/article/details/78881067

1.np.linspace() 生成(start,stop)区间指定元素个数num的list，均匀分布

Parameters

----------

start : scalar  #scalar：标量

The starting value of the sequence.

stop : scalar

The end value of the sequence, unless `endpoint` is set to False.

In that case, the sequence consists of all but the last of ``num + 1``

evenly spaced samples, so that `stop` is excluded.  Note that the step

size changes when `endpoint` is False.

num : int, optional  #oprional：可选项

Number of samples to generate. Default is 50. Must benon-negative.

endpoint : bool, optional  #是否包括右边界点

If True, `stop` is the last sample. Otherwise, it is not included.

Default is True.

retstep : bool, optional  #返回步长
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作者：IT_Shero
来源：CSDN
原文：https://blog.csdn.net/ui_shero/article/details/78881067
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np.linspace(2.0, 3.0, num=5, retstep=True)

(array([ 2.  ,  2.25,  2.5 ,  2.75,  3.  ]),0.25)

np.linspace(2.0, 3.0, num=5)

array([ 2.  ,  2.25,  2.5 ,  2.75,  3.  ])

np.linspace(2.0, 3.0, num=5, endpoint=False)

array([ 2. ,  2.2,  2.4,  2.6,  2.8])
--------------------------------

import numpy as np

import matplotlib.pyplot as plt

N = 8

y = np.zeros(N)

x1 = np.linspace(0, 10, N, endpoint=True)

x2 = np.linspace(0, 10, N, endpoint=False)

plt.plot(x1, y, 'o')

plt.plot(x2, y + 0.5, 'o')

plt.ylim([-0.5, 1]) #设置y轴区间

(-0.5, 1)

plt.show()

2.np.logspace() log分布间距生成list

Parameters
----------
start : float  #基底base的start次幂作为左边界
    ``base ** start`` is the starting value of the sequence.
stop : float  #基底base的stop次幂作为右边界
    ``base ** stop`` is the final value of the sequence, unless `endpoint`
    is False.  In that case, ``num + 1`` values are spaced over the
    interval in log-space, of which all but the last (a sequence of
    length ``num``) are returned.
num : integer, optional
    Number of samples to generate.  Default is 50.
endpoint : boolean, optional
    If true, `stop` is the last sample. Otherwise, it is not included.
    Default is True.
base : float, optional  #基底
    The base of the log space. The step size between the elements in
    ``ln(samples) / ln(base)`` (or ``log_base(samples)``) is uniform.
    Default is 10.0.
dtype : dtype
    The type of the output array.  If `dtype` is not given, infer the data
    type from the other input arguments.
---------------------

np.logspace(2.0, 3.0, num=4)

array([  100.        ,   215.443469  ,   464.15888336,  1000.        ])

np.logspace(2.0, 3.0, num=4, endpoint=False)

array([ 100.        ,  177.827941  ,  316.22776602,  562.34132519])

np.logspace(2.0, 3.0, num=4, base=2.0)

array([ 4.        ,  5.0396842 ,  6.34960421,  8.        ])
---------------------

import numpy as np

import matplotlib.pyplot as plt

N = 10

x1 = np.logspace(0.1, 1, N, endpoint=True)

x2 = np.logspace(0.1, 1, N, endpoint=False)

y = np.zeros(N)

plt.plot(x1, y, 'o')

plt.plot(x2, y + 0.5, '<')

plt.ylim([-0.5, 1])

(-0.5, 1)

plt.show()

3.np.arange() 生成(start,stop)区间指定步长step的list

np.arange(3)

array([0, 1, 2])

np.arange(3.0)

array([ 0.,  1.,  2.])

np.arange(3,7)

array([3, 4, 5, 6])

np.arange(3,7,2)

array([3, 5])