nlcpy.logspace

nlcpy.logspace(start, stop, num=50, endpoint=True, base=10.0, dtype=None, axis=0)

Returns numbers spaced evenly on a log scale.

In linear space, the sequence starts at base ** start (base to the power of start) and ends with base ** stop (see endpoint below).

Parameters

startarray_like

base ** start is the starting value of the sequence.

stoparray_like

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.

numint, optional

Number of samples to generate. Default is 50.

endpointbool, optional

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

basefloat, optional

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.

dtypedtype, optional

The type of the output array. If dtype is not given, infer the data type from the other input arguments.

axisint, optional

The axis in the result to store the samples. Relevant only if start or stop are array-like. By default (0), the samples will be along a new axis inserted at the beginning. Use -1 to get an axis at the end.

Returns

samplesndarray

num samples, equally spaced on a log scale.

参考

arange

Returns evenly spaced values within a given interval.

linspace

Returns evenly spaced numbers over a specified interval.

注釈

Logspace is equivalent to the code

>>> import nlcpy as vp
>>> y = vp.linspace(start, stop, num=num, endpoint=endpoint)
...  
>>> vp.power(base, y).astype(dtype)
...  

Examples

>>> import nlcpy as vp
>>> vp.logspace(2.0, 3.0, num=4)  
array([ 100.        ,  215.443469  ,  464.15888336, 1000.        ])
>>> vp.logspace(2.0, 3.0, num=4, endpoint=False) 
array([100.        , 177.827941  , 316.22776602, 562.34132519])
>>> vp.logspace(2.0, 3.0, num=4, base=2.0) 
array([4.        , 5.0396842 , 6.34960421, 8.        ])

Graphical illustration:

>>> import matplotlib.pyplot as plt
>>> N = 10
>>> x1 = vp.logspace(0.1, 1, N, endpoint=True)
>>> x2 = vp.logspace(0.1, 1, N, endpoint=False)
>>> y = vp.zeros(N)
>>> plt.plot(x1, y, 'o') 
>>> plt.plot(x2, y + 0.5, 'o') 
>>> plt.ylim([-0.5, 1])
(-0.5, 1.0)
>>> plt.show()