# numpy.geomspace¶

`numpy.``geomspace`(start, stop, num=50, endpoint=True, dtype=None)[源代码]

Return numbers spaced evenly on a log scale (a geometric progression).

This is similar to `logspace`, but with endpoints specified directly. Each output sample is a constant multiple of the previous.

Parameters: start : scalar The starting value of the sequence. stop : scalar 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. dtype : dtype The type of the output array. If `dtype` is not given, infer the data type from the other input arguments. samples : ndarray num samples, equally spaced on a log scale.

`logspace`
Similar to geomspace, but with endpoints specified using log and base.
`linspace`
Similar to geomspace, but with arithmetic instead of geometric progression.
`arange`
Similar to linspace, with the step size specified instead of the number of samples.

Notes

If the inputs or dtype are complex, the output will follow a logarithmic spiral in the complex plane. (There are an infinite number of spirals passing through two points; the output will follow the shortest such path.)

Examples

```>>> np.geomspace(1, 1000, num=4)
array([    1.,    10.,   100.,  1000.])
>>> np.geomspace(1, 1000, num=3, endpoint=False)
array([   1.,   10.,  100.])
>>> np.geomspace(1, 1000, num=4, endpoint=False)
array([   1.        ,    5.62341325,   31.6227766 ,  177.827941  ])
>>> np.geomspace(1, 256, num=9)
array([   1.,    2.,    4.,    8.,   16.,   32.,   64.,  128.,  256.])
```

Note that the above may not produce exact integers:

```>>> np.geomspace(1, 256, num=9, dtype=int)
array([  1,   2,   4,   7,  16,  32,  63, 127, 256])
>>> np.around(np.geomspace(1, 256, num=9)).astype(int)
array([  1,   2,   4,   8,  16,  32,  64, 128, 256])
```

Negative, decreasing, and complex inputs are allowed:

```>>> np.geomspace(1000, 1, num=4)
array([ 1000.,   100.,    10.,     1.])
>>> np.geomspace(-1000, -1, num=4)
array([-1000.,  -100.,   -10.,    -1.])
>>> np.geomspace(1j, 1000j, num=4)  # Straight line
array([ 0.   +1.j,  0.  +10.j,  0. +100.j,  0.+1000.j])
>>> np.geomspace(-1+0j, 1+0j, num=5)  # Circle
array([-1.00000000+0.j        , -0.70710678+0.70710678j,
0.00000000+1.j        ,  0.70710678+0.70710678j,
1.00000000+0.j        ])
```

Graphical illustration of `endpoint` parameter:

```>>> import matplotlib.pyplot as plt
>>> N = 10
>>> y = np.zeros(N)
>>> plt.semilogx(np.geomspace(1, 1000, N, endpoint=True), y + 1, 'o')
>>> plt.semilogx(np.geomspace(1, 1000, N, endpoint=False), y + 2, 'o')
>>> plt.axis([0.5, 2000, 0, 3])
>>> plt.grid(True, color='0.7', linestyle='-', which='both', axis='both')
>>> plt.show()
```