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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18.2
単純なモデル
313
最良の10モデルを元のデータに重ねると、いずれもかなりよいようです。
ggplot(sim1, aes(x, y)) +
geom_point(size = 2, color = "grey30") +
geom_abline(
aes(intercept = a1, slope = a2, color = -dist),
data = filter(grid, rank(dist) <= 10)
)
格子を細かくしていけば、最良モデルに絞り込むことができると考えるかもしれませんが、もっと
よい方法があります。Newton–Raphson探索（ニュートン法とも）という数値的最小化ツールです。
ニュートン法は直感的には極めて単純です。開始点を適当に取り、傾きの一番急なところを探します。
これ以上下がれないところに到達するまで曲線上を徐々に滑り降りていきます。Rでは、
optim()
で
これができます。
best <- optim(c(0, 0), measure_distance, data = sim1)
best$par
#> [1] 4.22 2.05
ggplot(sim1, aes(x, y)) +
314
18
章
modelr
を使ったモデルの基本
geom_point(size ...
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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.