1 % Created 2010-11-07 Sun 15:18

     2 \documentclass[presentation]{beamer}

     3 \usepackage[latin1]{inputenc}

     4 \usepackage[T1]{fontenc}

     5 \usepackage{fixltx2e}

     6 \usepackage{graphicx}

     7 \usepackage{longtable}

     8 \usepackage{float}

     9 \usepackage{wrapfig}

    10 \usepackage{soul}

    11 \usepackage{t1enc}

    12 \usepackage{textcomp}

    13 \usepackage{marvosym}

    14 \usepackage{wasysym}

    15 \usepackage{latexsym}

    16 \usepackage{amssymb}

    17 \usepackage{hyperref}

    18 \tolerance=1000

    19 \usepackage[english]{babel} \usepackage{ae,aecompl}

    20 \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}

    21 \usepackage{listings}

    22 \lstset{language=Python, basicstyle=\ttfamily\bfseries,

    23 commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},

    24 showstringspaces=false, keywordstyle=\color{blue}\bfseries}

    25 \providecommand{\alert}[1]{\textbf{#1}}

    26 

    27 \title{Getting started with arrays}

    28 \author{FOSSEE}

    29 \date{}

    30 

    31 \usetheme{Warsaw}\usecolortheme{default}\useoutertheme{infolines}\setbeamercovered{transparent}

    32 \begin{document}

    33 

    34 \maketitle

    35 

    36 

    37 

    38 

    39 

    40 

    41 

    42 

    43 

    44 \begin{frame}

    45 \frametitle{Outline}

    46 \label{sec-1}

    47 

    48 \begin{itemize}

    49 \item Arrays

    50 

    51 \begin{itemize}

    52 \item why arrays over lists

    53 \end{itemize}

    54 

    55 \item Creating arrays

    56 \item Array operations

    57 \end{itemize}

    58 \end{frame}

    59 \begin{frame}

    60 \frametitle{Overview of Arrays}

    61 \label{sec-2}

    62 

    63 \begin{itemize}

    64 \item Arrays are homogeneous data structures.

    65 

    66 \begin{itemize}

    67 \item elements have to the same data type

    68 \end{itemize}

    69 

    70 \item Arrays are faster compared to lists

    71 

    72 \begin{itemize}

    73 \item at least \emph{80-100 times} faster than lists

    74 \end{itemize}

    75 

    76 \end{itemize}

    77 \end{frame}

    78 \begin{frame}[fragile]

    79 \frametitle{Creating Arrays}

    80 \label{sec-3}

    81 

    82 \begin{itemize}

    83 \item Creating a 1-dimensional array

    84 \end{itemize}

    85 

    86 \begin{verbatim}

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

    88 \end{verbatim}

    89 

    90   \texttt{[1, 2, 3, 4]} is a list.

    91 \end{frame}

    92 \begin{frame}[fragile]

    93 \frametitle{Creating two-dimensional array}

    94 \label{sec-4}

    95 

    96 \begin{itemize}

    97 \item Creating a 2-dimensional array

    98 \end{itemize}

    99 

   100 \begin{verbatim}

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

   102 \end{verbatim}

   103 

   104   here we convert a list of lists to an array making a 2-d array.

   105 \begin{itemize}

   106 \item Easier method of creating array with consecutive elements.

   107 \end{itemize}

   108 

   109 \begin{verbatim}

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

   111 \end{verbatim}

   112 \end{frame}

   113 \begin{frame}[fragile]

   114 \frametitle{\texttt{reshape()} method}

   115 \label{sec-5}

   116 

   117 \begin{itemize}

   118 \item To reshape an array

   119 \end{itemize}

   120 

   121 \begin{verbatim}

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

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

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

   125 \end{verbatim}

   126 \end{frame}

   127 \begin{frame}[fragile]

   128 \frametitle{Creating \texttt{array} from \texttt{list}.}

   129 \label{sec-6}

   130 

   131 \begin{itemize}

   132 \item \texttt{array()} method accepts list as argument

   133 \item Creating a list

   134 \begin{verbatim}

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

   136 \end{verbatim}

   137 

   138 \item Creating an array

   139 \begin{verbatim}

   140      In []: a3 = array(l1)

   141 \end{verbatim}

   142 

   143 \end{itemize}

   144 \end{frame}

   145 \begin{frame}

   146 \frametitle{Exercise 1}

   147 \label{sec-7}

   148 

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

   150 \end{frame}

   151 \begin{frame}[fragile]

   152 \frametitle{\texttt{.shape} of array}

   153 \label{sec-8}

   154 

   155 \begin{itemize}

   156 \item \texttt{.shape}

   157     To find the shape of the array

   158 \begin{verbatim}

   159      In []: a1.shape

   160 \end{verbatim}

   161 

   162 \item \texttt{.shape}

   163     returns a tuple of shape

   164 \end{itemize}

   165 \end{frame}

   166 \begin{frame}

   167 \frametitle{Exercise 2}

   168 \label{sec-9}

   169 

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

   171 \end{frame}

   172 \begin{frame}[fragile]

   173 \frametitle{Homogeneous data}

   174 \label{sec-10}

   175 

   176 \begin{itemize}

   177 \item All elements in array should be of same type

   178 \begin{verbatim}

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

   180 \end{verbatim}

   181 

   182 \end{itemize}

   183 \end{frame}

   184 \begin{frame}[fragile]

   185 \frametitle{Implicit type casting}

   186 \label{sec-11}

   187 

   188 \begin{verbatim}

   189     In []: a4

   190 \end{verbatim}

   191 

   192     All elements are type casted to string type

   193 \end{frame}

   194 \begin{frame}

   195 \frametitle{\texttt{identity()}, \texttt{zeros()} methods}

   196 \label{sec-12}

   197 

   198 \begin{itemize}

   199 \item \texttt{identity(n)}

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

   201 \item \texttt{zeros((m, n))}

   202     Creates an \texttt{m X n} matrix with all elements 0.

   203 \end{itemize}

   204 \end{frame}

   205 \begin{frame}

   206 \frametitle{Learning exercise}

   207 \label{sec-13}

   208 

   209 \begin{itemize}

   210 \item Find out about

   211 

   212 \begin{itemize}

   213 \item \texttt{zeros\_like()}

   214 \item \texttt{ones()}

   215 \item \texttt{ones\_like()}

   216 \end{itemize}

   217 

   218 \end{itemize}

   219 \end{frame}

   220 \begin{frame}

   221 \frametitle{Array operations}

   222 \label{sec-14}

   223 

   224 \begin{itemize}

   225 \item \texttt{a1 * 2}

   226     returns a new array with all elements of \texttt{a1} multiplied by \texttt{2}.

   227 

   228 \begin{itemize}

   229 \item Similarly \texttt{+}, \texttt{-} \& \texttt{/}.

   230 \end{itemize}

   231 

   232 \item \texttt{a1 + 2}

   233     returns a new array with all elements of \texttt{a1} summed with \texttt{2}.

   234 \item \texttt{a1 += 2}

   235     adds \texttt{2} to all elements of array \texttt{a1}.

   236 

   237 \begin{itemize}

   238 \item Similarly \texttt{-=}, \texttt{*=} \& \texttt{/=}.

   239 \end{itemize}

   240 

   241 \item \texttt{a1 + a2}

   242     does elements-wise addition.

   243 

   244 \begin{itemize}

   245 \item Similarly \texttt{-}, \texttt{*} \& \texttt{/}.

   246 \end{itemize}

   247 

   248 \item \texttt{a1 * a2}

   249     does element-wise multiplication

   250 \end{itemize}

   251 

   252 

   253   \textbf{Note} - array(A) * array(B) does element wise multiplication and not matrix multiplication

   254 \end{frame}

   255 \begin{frame}

   256 \frametitle{Summary}

   257 \label{sec-15}

   258 

   259   In this tutorial we covered,

   260 \begin{itemize}

   261 \item Basics of arrays

   262 \item Creating arrays

   263 \item Arrays from lists

   264 \item Basic array operations

   265 \end{itemize}

   266 \end{frame}

   267 \begin{frame}

   268 \frametitle{Thank you!}

   269 \label{sec-16}

   270 

   271   \begin{block}{}

   272   \begin{center}

   273   This spoken tutorial has been produced by the

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

   275   \end{center}

   276   \begin{center}

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

   278       Information \& Communication Technology \\ 

   279       MHRD, Govt. of India}.

   280   \end{center}  

   281   \end{block}

   282 \end{frame}

   283 

   284 \end{document}