Machine Learning - Standard Deviation
Kwani ne standard deviation?
Standard deviation (Standard Deviation, kuma kuma yana kira mean variance) ita:
Standard deviation da yake da kwayar:
Standard deviation da yake da girma:
Misali: dukiyar da na gina kwayar 7 mota:
speed = [86,87,88,86,87,85,86]
Standard deviation ita:
0.9
Ina nufin: kaiyaki na yadda da ke cikin yadda na 0.9, kuma 86.4.
Duba: a kara da gina kwayar nufin da yake da kwayar:
speed = [32,111,138,28,59,77,97]
Standard deviation ita:
37.85
Ina nufin: kaiyaki na yadda da ke cikin kwayar yadda (yadda ita 77.4) 37.85.
Duba: kaiyaki na standard deviation da yake da girma:
NumPy modul da ke da hanci don kara standard deviation:
实例
Kama ka wajen: NumPy std() Fannan kowace: nuna standard deviation:
import numpy speed = [86,87,88,86,87,85,86] x = numpy.std(speed) print(x)
实例
import numpy speed = [32,111,138,28,59,77,97] x = numpy.std(speed) print(x)
Variance
Variance ita daya dake bayanin nufin: nuna da kwayar daga yadda:
Dan da yake amfana da root na variance, a zai gana standard deviation!
Ma kuma, kama ka kara standard deviation kara yadda, a zai gana variance!
Kung gana kara variance, ka mabaya ka wajen:
1. Fannan kowace: kira yadda:
(32+111+138+28+59+77+97) / 7 = 77.4
2. Fannan kowace: aro da yadda:
32 - 77.4 = -45.4 111 - 77.4 = 33.6 138 - 77.4 = 60.6 28 - 77.4 = -49.4 59 - 77.4 = -18.4 77 - 77.4 = - 0.4 97 - 77.4 = 19.6
3. Fannan kowace: aro da farkin:
(-45.4)2 = 2061.16 (33.6)2 = 1128.96 (60.6)2 = 3672.36 (-49.4)2 = 2440.36 (-18.4)2 = 338.56 (- 0.4)2 = 0.16 (19.6)2 = 384.16
4. 方差是这些平方差的平均值：
(2061.16+1128.96+3672.36+2440.36+338.56+0.16+384.16) / 7 = 1432.2
幸运的是，NumPy 有一种计算方差的方法：
实例
使用 NumPy var() 方法确定方差：
import numpy speed = [32,111,138,28,59,77,97] x = numpy.var(speed) print(x)
标准差
如我们所知，计算标准差的公式是方差的平方根：
√ 1432.25 = 37.85
或者，如上例所示，使用 NumPy 计算标准差：
实例
请使用 NumPy std() 方法查找标准差：
import numpy speed = [32,111,138,28,59,77,97] x = numpy.std(speed) print(x)
符号
标准差通常用 Sigma 符号表示：σ
方差通常由 Sigma Square 符号 σ2 表示
章节总结
标准差和方差是机器学习中经常使用的术语，因此了解如何获取它们以及它们背后的概念非常重要。
