November 2018
Intermediate to advanced
272 pages
6h 51m
Japanese
book
エレガントなSciPy ―Pythonによる科学技術計算
by Juan Nunez-Iglesias, Stéfan van der Walt, Harriet Dashnow, 山崎 邦子, 山崎 康宏
Content preview from エレガントなSciPy ―Pythonによる科学技術計算
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79
4
章
周波数と高速フーリエ変換
宇宙の仕組みを発見したいなら、エネルギー、周波数、振動の観点から考えよ。
―
ニコラ・テスラ
4
章は、著者
SW
の父親である
PW van der Walt
と共同執筆したものです。
本書の他の章とは少々異なった形式をとっています。特に、コードが控えめだと思われるかもし
れません。代わりに本章では、エレガントなアルゴリズムである高速フーリエ変換（
Fast Fourier
Transform
：
FFT
）をじっくりと解説します。
FFT
は非常に役立つので、
SciPy
にも実装されてお
り、もちろん
NumPy
配列にも使えます。
4.1
周波数とは
まずは、プロットのスタイルの設定から始めましょう。いつものモジュールもインポートしま
す。
# Make plots appear inline, set custom plotting style
%matplotlib inline
プロットをインライン表示させ、本書独自のプロットスタイルを設定する。
import matplotlib.pyplot as plt
plt.style.use('style/elegant.mplstyle')
import numpy as np
離散フーリエ変換（
Discrete Fourier Transform
：
DFT
）
†
は、時間もしくは空間データを周波数
領域のデータに変換する数学的手法です。周波数（
frequency
）という用語は、英語の日常生活用
語として（訳注：回数、頻度の意味で）よく使われるため、 ...
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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.