June 2024
Intermediate to advanced
200 pages
4h 46m
Japanese
Content preview from Python2年生 データ分析のしくみ 第2版 体験してわかる！会話でまなべる！
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65
データのどこを使う？
LESSON
06
条件でデータを抽出する
列データから「ある条件に合うデータを抽出」することもできます。
「ある条件に合うかどうか」は、等号や不等号（
=、<、>）を使うだけで調べることがで
きます。条件に合うものは
True、合わないものはFalseになります。
データフレーム["列名"] = 値
データフレーム
["列名"] > 値
データフレーム
["列名"] < 値
「国語が80より大きいか」を調べてみましょう（リスト2.24）。
dfA = pd.read_csv("test.csv", index_col=0)
dfA["
国語"] > 80
名前
A太 True
B
介 False
C
子 True
D
郎 False
E
美 True
F
菜 True
Name:
国語, dtype: bool
80より大きい場合だけ、Trueになりました。これは、「条件に合うかどうかのTrue・False
のシリーズ（1次元データ）」 です。このシリーズを使うとTrueの行だけ抽出することがで
きます。つまり、「データフレーム
= データフレーム[条件に合うかどうかのTrue・Falseの
書式：条件に合うかどうか調べる
【入力プログラム】リスト 2.24
出力結果
条件を指定すれば、その
データが条件に合うとき
だけ、
True
になるんだ。
Chapter
2
66
シリーズ]」と命令すると、「条件に合った行だけ抽出」することができるのです。
「国語が
80より大きい行だけ抽出」してみましょう（リスト2.25）。
データフレーム =
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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.