📅 最后修改于: 2020-11-08 07:35:02 🧑 作者: Mango
在本章中，我们将看到如何从数值范围创建数组。
此函数返回一个ndarray对象，该对象包含给定范围内的均匀间隔的值。该函数的格式如下-
numpy.arange(start, stop, step, dtype)
构造函数采用以下参数。
| Sr.No. | Parameter & Description |
|---|---|
| 1 |
start The start of an interval. If omitted, defaults to 0 |
| 2 |
stop The end of an interval (not including this number) |
| 3 |
step Spacing between values, default is 1 |
| 4 |
dtype Data type of resulting ndarray. If not given, data type of input is used |
以下示例显示如何使用此函数。
import numpy as np
x = np.arange(5)
print x
其输出如下-
[0 1 2 3 4]
import numpy as np
# dtype set
x = np.arange(5, dtype = float)
print x
在这里，输出将是-
[0. 1. 2. 3. 4.]
# start and stop parameters set
import numpy as np
x = np.arange(10,20,2)
print x
其输出如下-
[10 12 14 16 18]
此函数类似于arange()函数。在此函数，将指定间隔之间的均匀间隔数，而不是步长。此函数的用法如下-
numpy.linspace(start, stop, num, endpoint, retstep, dtype)
构造函数采用以下参数。
| Sr.No. | Parameter & Description |
|---|---|
| 1 |
start The starting value of the sequence |
| 2 |
stop The end value of the sequence, included in the sequence if endpoint set to true |
| 3 |
num The number of evenly spaced samples to be generated. Default is 50 |
| 4 |
endpoint True by default, hence the stop value is included in the sequence. If false, it is not included |
| 5 |
retstep If true, returns samples and step between the consecutive numbers |
| 6 |
dtype Data type of output ndarray |
以下示例演示了linspace函数的用法。
import numpy as np
x = np.linspace(10,20,5)
print x
它的输出将是-
[10. 12.5 15. 17.5 20.]
# endpoint set to false
import numpy as np
x = np.linspace(10,20, 5, endpoint = False)
print x
输出将是-
[10. 12. 14. 16. 18.]
# find retstep value
import numpy as np
x = np.linspace(1,2,5, retstep = True)
print x
# retstep here is 0.25
现在，输出将是-
(array([ 1. , 1.25, 1.5 , 1.75, 2. ]), 0.25)
此函数返回一个ndarray对象，该对象包含在对数刻度上均匀间隔的数字。标度的起点和终点是基准的索引，通常为10。
numpy.logspace(start, stop, num, endpoint, base, dtype)
以下参数确定logspace函数的输出。
| Sr.No. | Parameter & Description |
|---|---|
| 1 |
start The starting point of the sequence is basestart |
| 2 |
stop The final value of sequence is basestop |
| 3 |
num The number of values between the range. Default is 50 |
| 4 |
endpoint If true, stop is the last value in the range |
| 5 |
base Base of log space, default is 10 |
| 6 |
dtype Data type of output array. If not given, it depends upon other input arguments |
以下示例将帮助您了解日志空间函数。
import numpy as np
# default base is 10
a = np.logspace(1.0, 2.0, num = 10)
print a
其输出如下-
[ 10. 12.91549665 16.68100537 21.5443469 27.82559402
35.93813664 46.41588834 59.94842503 77.42636827 100. ]
# set base of log space to 2
import numpy as np
a = np.logspace(1,10,num = 10, base = 2)
print a
现在，输出将是-
[ 2. 4. 8. 16. 32. 64. 128. 256. 512. 1024.]