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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139
データのばらつきを数値で表す
LESSON
15
print(df.var())
分散の値が表示されました。すべての列データの分散を求めるので、IDの分散まで表示
されますが、
AとBの値にだけ注目しましょう。ただ、「0〜100の間のデータのばらつき」
を知りたかったのに、
430といった大きな値ですね。
これは分散が「
2乗した値」を使っているからで、もとの値が大きければ結果もどんど
ん大きくなっていきます。そこで、「
2乗したのだから、平方根でもとの単位に戻そう」と
いう方法が考えられました。それが「標準偏差」です。
データの個数
「分散」の平方根
「標準偏差」
ちょうどいい
大きさ
計算では、「分散の平方根」で求めます。
標準偏差＝ 分散
pandasでは、「データフレーム.std()」と命令します。試してみましょう（リスト5.4）。
【入力プログラム】リスト 5.3
出力結果
ID 9.166667
A 430.666667
B 12.888889
dtype: float64
標準偏差は
このようにして
求められるよ！
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