October 2017
Intermediate to advanced
480 pages
9h 49m
Japanese
Content preview from Rではじめるデータサイエンス
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18.4
フォーミュラとモデルファミリー
327
これによって、2連続変数間の交互作用が基本的にはカテゴリ変数と連続変数との交互作用と同じ
だということが示されます。交互作用は、固定オフセットがないことを示します。
y
を予測するには、
x1
と
x2
の値を同時に考えます。
2つの連続変数だけでも、よい可視化が難しいことがわかります。それは当然です。3変数以上が
同時に交互作用をどのようにするか理解することが容易だと期待すべきではありません。それでも、
少しでも助かるのは、探索のためにモデルを使っており、モデルを徐々に構築することができるから
です。モデルが完全である必要はありません。データについてなにがしかを明らかにすることを助け
るだけでよいのです。
mod2
の方が
mod1
よりよいかどうかと、私は残差を調べてみました。その通りだと私は思いますが、
結構微妙なところです。読者は練習問題として検討してください。
18.4.4
変換
モデルフォーミュラの中で変換もできます。例えば、
log(y) ~ sqrt(x1) + x2
は
log(y) = a_1
+ a_2 * sqrt(x1) + a_3 * x2
に変換されます。変換が
+
,
*
,
^
,
-
を含むなら、
I()
でラップして、R
がモデル指定の一部と間違えないようにします。例えば、
y ~ x + I(x ^ 2)
は
y = a_1 + a_2 * x
328
18
章
modelr
を使ったモデルの基本
+ a_3 * x ^ 2
と翻訳されます。
I()
を忘れて
y ~ x ...
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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.