np.linspace() np.logspace() np.arange() 区别

 np.linspace() np.logspace() np.arange() 区别

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

Signature: np.linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None) Docstring: Return evenly spaced numbers over a specified interval.   Returns `num` evenly spaced samples, calculated over the interval [`start`, `stop`].   The endpoint of the interval can optionally be excluded.   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   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])       If True, return (`samples`, `step`), where `step` is the spacing     between samples. dtype : dtype, optional     The type of the output array.  If `dtype` is not given, infer the data     type from the other input arguments. # Graphical illustration: 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

Signature: np.logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None) Docstring: Return numbers spaced evenly on a log scale. 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. Returns ------- samples : ndarray     `num` samples, equally spaced on a log scale. Examples -------- 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.        ])   Notes ----- Logspace is equivalent to the code: y = np.linspace(start, stop, num=num, endpoint=endpoint) power(base, y).astype(dtype)       # Graphical illustration: 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])   Docstring: arange([start,] stop[, step,], dtype=None) Return evenly spaced values within a given interval.   When using a non-integer step, such as 0.1, the results will often not be consistent.  It is better to use ``linspace`` for these cases.     Parameters ---------- start : number, optional     Start of interval.  The interval includes this value.  The default     start value is 0. stop : number     End of interval.  The interval does not include this value, except     in some cases where `step` is not an integer and floating point     round-off affects the length of `out`.  # round-off:四舍五入 step : number, optional     Spacing between values.  For any output `out`, this is the distance     between two adjacent values, ``out[i+1] - out[i]``.  The default     step size is 1. If `step` is specified, `start` must also be given.# adjacent:相邻 dtype : dtype     The type of the output array.  If `dtype` is not given, infer the data     type from the other input arguments.   Returns ------- arange : ndarray     Array of evenly spaced values.       For floating point arguments, the length of the result is     ``ceil((stop - start)/step)``.  Because of floating point overflow,     this rule may result in the last element of `out` being greater     than `stop`.  #ceil()：向上取整