November 2019
Intermediate to advanced
472 pages
9h 23m
Japanese
Content preview from Rグラフィックスクックブック 第2版 ―ggplot2によるグラフ作成のレシピ集
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364
14
章 文書用に図を出力する
レシピ
14.5
ビットマップファイル（
PNG/TIFF
）への出力
問題
図のビットマップを作成し、
PNG
ファイルに保存したい。
解決策
PNG
ビットマップファイルに出力する方法は
2
つあります。
1
つ目は
PNG
グラフィックスデバイスを
png()
で開き、
dev.off()
でデバイスを閉じる方法です。
base
パッケージで作成した図を始めとして
ggplot2
や
lattice
などで作られるグリッドベースの図など、
R
で作ることができるほとんどの図でこの方
法が使えます。
#
幅と高さはピクセル指定
png("myplot.png", width = 400, height = 400)
#
プロット
plot(mtcars$wt, mtcars$mpg)
dev.off()
複数の図を出力するにはファイル名に
%d
を入れます。これが
1
、
2
、
3
といった連番に置き換えられま
す。
#
幅と高さはピクセル指定
png("myplot-%d.png", width = 400, height = 400)
plot(mtcars$wt, mtcars$mpg)
print(ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point())
dev.off()
ggplot
オブジェクトに対して
print()
を呼び出していることに注目しましょう。これはコードをスク
リプト中から実行しても確実に図が出力されるようにするためです。
幅と高さはピクセルで、デフォルトでは
72
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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.