August 2019
Beginner to intermediate
232 pages
3h 50m
Chinese
Content preview from Web容量规划之美
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122
第
4
章
在寻求最符合你的数据的数学公式时
，
最好避开高阶多项式
。
高阶多项式拟合
结果
（
决定系数
）
很好
，
这看起来很诱人
，
但任何高于二阶的任何多项式都会
出现特定数据集外的动态波动
。
这是通常所说的过度拟合统计学习和机器学习
。
样条曲线是一种常见的曲线拟合模型
。
在线性和非线性拟合中存在大量的工作
。
有关本专题先前研究工作的参考资料
，
请参考本章后面的
“
延展阅读
”。
预测的时间长短通常是按具体情况确定的
。
例如
，
小型初创公司可能只需要知
道未来三个月需要花多少钱
。
相反
，
大型知名企业需要为今年剩余时间做资本
支出的预估
。
总体而言
，
受底层特征的影响
，
预测时间越长
，
预测的准确性就
越低
。
这个例子告诉我们
，
在曲线拟合的时候要多用尝试
，
不要一味追求完美匹配
，
因为它们通常是有问题的假设结果
。
当然，你希望把趋势线延伸到未来。趋势线应该延伸到足够远，使它与我们的总
可用空间相交。这就是你可以预测空间将耗尽的地方。在对话框的预测部分，键
入
25
个值单位。我们这个示例的单位是天。单击
OK
后，预测应该类似图
4-6
所示。
图
4
-
6
：延伸趋势线
123
趋势预测
如图
4-6
所示，在第
37
天左右我们将耗尽磁盘空间。所幸我们有用于绘制趋势线
的公式，并不需要反复看图来找到真实值。表
4-1
详细描述了这一过程：首先在
Excel
中插入公式，然后用单位“天”作为 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.