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    20 

    21 #+TITLE: Getting started with arrays

    22 #+AUTHOR: FOSSEE

    23 #+EMAIL: info@fossee.in

    24 #+DATE:    

    25 

    26 #+DESCRIPTION: 

    27 #+KEYWORDS: 

    28 #+LANGUAGE:  en

    29 #+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t

    30 #+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc

    31 

    32 * Outline

    33   - Arrays

    34     - why arrays over lists

    35   - Creating arrays

    36   - Array operations

    37 

    38 * Overview of Arrays

    39   - Arrays are homogeneous data structures.

    40     - elements have to the same data type

    41   - Arrays are faster compared to lists

    42     - at least /80-100 times/ faster than lists

    43 

    44 * Creating Arrays

    45   - Creating a 1-dimensional array

    46   : In []: a1 = array([1, 2, 3, 4])

    47   - Creating a 2-dimensional array

    48   : In []: a2 = array([[1,2,3,4],[5,6,7,8]])

    49   - Easier method of creating array with consecutive elements.

    50   : In []: ar = arange(1,9)

    51 * ~reshape()~ method

    52   - To reshape an array

    53   : In []: ar.reshape(2, 4)

    54   : In []: ar.reshape(4, 2)

    55   : In []: ar = ar.reshape(2, 4)

    56 

    57 * Creating ~array~ from ~list~.

    58   - ~array()~ method accepts list as argument

    59   - Creating a list

    60    : In []: l1 = [1, 2, 3, 4]

    61   - Creating an array

    62     : In []: a3 = array(l1)

    63 

    64 * Exercise 1

    65   Create a 3-dimensional array of the order (2, 2, 4).

    66 

    67 * ~.shape~ of array

    68   - ~.shape~

    69     To find the shape of the array

    70     : In []: a1.shape

    71   - ~.shape~

    72     returns a tuple of shape

    73 * Exercise 2

    74   Find out the shape of the other arrays(a2, a3, ar) that we have created.

    75 * Homogeneous data

    76   - All elements in array should be of same type

    77     : In []: a4 = array([1,2,3,'a string'])

    78 * Implicit type casting 

    79    : In []: a4

    80     All elements are type casted to string type

    81 * ~identity()~, ~zeros()~ methods

    82   - ~identity(n)~

    83     Creates an identity matrix, a square matrix of order (n, n) with diagonal elements 1 and others 0.

    84   - ~zeros((m, n))~

    85     Creates an ~m X n~ matrix with all elements 0.

    86 

    87 * Learning exercise

    88   - Find out about

    89     - ~zeros_like()~

    90     - ~ones()~

    91     - ~ones_like()~

    92 

    93 * Array operations

    94   - ~a1 * 2~

    95     returns a new array with all elements of ~a1~ multiplied by ~2~.

    96     - Similarly ~+~, ~-~ \& ~/~.

    97   - ~a1 + 2~

    98     returns a new array with all elements of ~a1~ summed with ~2~.

    99   - ~a1 += 2~

   100     adds ~2~ to all elements of array ~a1~.

   101     - Similarly ~-=~, ~*=~ \& ~/=~.

   102   - ~a1 + a2~

   103     does elements-wise addition.

   104     - Similarly ~-~, ~*~ \& ~/~.

   105   - ~a1 * a2~

   106     does element-wise multiplication

   107 

   108   *Note* - array(A) * array(B) does element wise multiplication and not matrix multiplication

   109 

   110 * Summary

   111   In this tutorial we covered,

   112   - Basics of arrays

   113   - Creating arrays

   114   - Arrays from lists

   115   - Basic array operations

   116 

   117 * Thank you!

   118 #+begin_latex

   119   \begin{block}{}

   120   \begin{center}

   121   This spoken tutorial has been produced by the

   122   \textcolor{blue}{FOSSEE} team, which is funded by the 

   123   \end{center}

   124   \begin{center}

   125     \textcolor{blue}{National Mission on Education through \\

   126       Information \& Communication Technology \\ 

   127       MHRD, Govt. of India}.

   128   \end{center}  

   129   \end{block}

   130 #+end_latex

   131 

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