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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15.3
関数は人間とコンピュータのためのもの
241
is_directory <- function(x) file.info(x)$isdir
is_readable <- function(x) file.access(x, 4) == 0
7. 「Little bunny Foo Foo」の 完 全 な 歌 詞（http://bit.ly/littlebunnyfoofooま た は https://www.
kididdles.com/lyrics/l007.htmlなどを参照）を読むこと。この歌には繰り返しが多い。前章のパ
イプの例を拡張して、歌詞全体に対応するようにして、関数を使い重複を減らしなさい。
15.3
関数は人間とコンピュータのためのもの
関数がコンピュータのためだけではなく、人間のためでもあることを意識しましょう。Rは関数が
何と呼ばれるか、どのような注釈を含むかは考慮しませんが、人間の読み手にとっ
ては、名前と注
釈は重要です。本節では、人間が理解できるような関数を書くときに心に留めておくべきことについ
て述べます。
関数名は重要です。関数名は簡潔で、しかも関数の行うことを明確に示すことが理想ですが、簡
単ではありません。RStudioの補完機能が長い名前の入力を容易にするので、短いよりは明確な方が
よい名前です。
一般に、関数名には動詞、引数には名詞を使いますが、例外があります。名詞の関数名は次のよ
うな場合です。よく知られた名詞の内容を計算する場合（例：
mean()
は
compute_mean() ...
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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.