Book Image

NumPy Beginner's Guide - Second Edition

By : Ivan Idris
Book Image

NumPy Beginner's Guide - Second Edition

By: Ivan Idris

Overview of this book

NumPy is an extension to, and the fundamental package for scientific computing with Python. In today's world of science and technology, it is all about speed and flexibility. When it comes to scientific computing, NumPy is on the top of the list. NumPy Beginner's Guide will teach you about NumPy, a leading scientific computing library. NumPy replaces a lot of the functionality of Matlab and Mathematica, but in contrast to those products, is free and open source. Write readable, efficient, and fast code, which is as close to the language of mathematics as is currently possible with the cutting edge open source NumPy software library. Learn all the ins and outs of NumPy that requires you to know basic Python only. Save thousands of dollars on expensive software, while keeping all the flexibility and power of your favourite programming language.You will learn about installing and using NumPy and related concepts. At the end of the book we will explore some related scientific computing projects. This book will give you a solid foundation in NumPy arrays and universal functions. Through examples, you will also learn about plotting with Matplotlib and the related SciPy project. NumPy Beginner's Guide will help you be productive with NumPy and have you writing clean and fast code in no time at all.
Table of Contents (19 chapters)
Numpy Beginner's Guide Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – smoothing stock prices with the Blackman window


Let's smooth the close prices from the small AAPL stock prices data file. Perform the following steps to do so:

  1. Load the data into a NumPy array. Call the NumPy blackman function to form a window and then use this window to smooth the price signal.

    closes=np.loadtxt('AAPL.csv', delimiter=',', usecols=(6,), converters={1:datestr2num}, unpack=True)
    N = int(sys.argv[1])
    window = np.blackman(N)
    smoothed = np.convolve(window/window.sum(),
      closes, mode='same')
  2. Plot the smoothed prices with Matplotlib. We will omit the first five and the last five data points in this example. The reason for this is that there is a strong boundary effect.

    plot(smoothed[N:-N], lw=2, label="smoothed")
    plot(closes[N:-N], label="closes")
    legend(loc='best')
    show()

    The closing prices of AAPL smoothed with the Blackman window should appear, as follows:

What just happened?

We plotted the closing price of AAPL from our sample data file that was smoothed using...