我如何将浮点数限制在一个极限之下? [英] How do I clip a floating-point number to just below a limit?
问题描述
像 numpy。 random.uniform()
返回两个边界之间的浮点值,包括第一个边界,但不包括顶部边界。也就是说, numpy.random.uniform(0,1)
可能会产生0,但永远不会产生1.
我正在采取这样的数字,并使用函数来处理它们,有时会返回范围之外的结果。我可以使用 numpy.clip()
将范围之外的值切回到0-1,但是不幸的是,这个限制是顶部数字的包括。
如何在python中指定数目无限小于1?
'使用numpy,你可以简单地使用 numpy.nextafter :
>>> import numpy
>>> numpy.nextafter(1,0)
0.99999999999999989
请注意(至少对我而言) :
>>> import sys
>>> 1-sys.float_info.epsilon
0.9999999999999998
>>> numpy.nextafter(1,0) - (1-sys.float_info.epsilon)
1.1102230246251565e-16
>>> numpy.nextafter(1,0)> (1-sys.float_info.epsilon)
True
顺便说一句,对于@Robert Kern指出有时random.uniform 将包含除(0,1)以外的一些输入的上界:
>>> import random,numpy
>>> numpy.nextafter(0,1)
4.9406564584124654e-324
>>> random.uniform(0,numpy.nextafter(0,1))
0.0
>>> random.uniform(0,numpy.nextafter(0,1))
0.0
>>> random.uniform(0,numpy.nextafter(0,1))
4.9406564584124654e-324
< [我同意一般意义上说,可能有更好的方法来解决这个问题。]
Functions like numpy.random.uniform()
return floating point values between a two bounds, including the first bound but excluding the top one. That is, numpy.random.uniform(0,1)
may yield 0 but will never result in 1.
I'm taking such numbers and processing them with a function that sometimes returns results outside of the range. I can use numpy.clip()
to chop values outside of the range back to 0-1, but unfortunately that limit is inclusive of the top number.
How do I specify "the number infinitesimally smaller than 1" in python?
Well, if you're using numpy, you can simply use numpy.nextafter:
>>> import numpy
>>> numpy.nextafter(1, 0)
0.99999999999999989
Note that (at least for me):
>>> import sys
>>> 1-sys.float_info.epsilon
0.9999999999999998
>>> numpy.nextafter(1, 0) - (1-sys.float_info.epsilon)
1.1102230246251565e-16
>>> numpy.nextafter(1, 0) > (1-sys.float_info.epsilon)
True
Incidentally, to second @Robert Kern's point that sometimes random.uniform will include the upper bound for some inputs other than (0, 1):
>>> import random, numpy
>>> numpy.nextafter(0,1)
4.9406564584124654e-324
>>> random.uniform(0, numpy.nextafter(0,1))
0.0
>>> random.uniform(0, numpy.nextafter(0,1))
0.0
>>> random.uniform(0, numpy.nextafter(0,1))
4.9406564584124654e-324
[I share the general sense that there is probably a better way to approach this problem.]
这篇关于我如何将浮点数限制在一个极限之下?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!