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

\title{Getting started with arrays}

\author{FOSSEE}

\date{}

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

\begin{document}

\maketitle

\begin{frame}

\frametitle{Outline}

\label{sec-1}

\begin{itemize}

\item Arrays

\begin{itemize}

\item why arrays over lists

\end{itemize}

\item Creating arrays

\item Array operations

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Overview of Arrays}

\label{sec-2}

\begin{itemize}

\item Arrays are homogeneous data structures.

\begin{itemize}

\item elements have to the same data type

\end{itemize}

\item Arrays are faster compared to lists

\begin{itemize}

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

\end{itemize}

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Creating Arrays}

\label{sec-3}

\begin{itemize}

\item Creating a 1-dimensional array

\end{itemize}

\begin{verbatim}

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

\end{verbatim}

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

\end{frame}

\begin{frame}[fragile]

\frametitle{Creating two-dimensional array}

\label{sec-4}

\begin{itemize}

\item Creating a 2-dimensional array

\end{itemize}

\begin{verbatim}

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

\end{verbatim}

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

\begin{itemize}

\item Easier method of creating array with consecutive elements.

\end{itemize}

\begin{verbatim}

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

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

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

\label{sec-5}

\begin{itemize}

\item To reshape an array

\end{itemize}

\begin{verbatim}

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

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

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

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

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

\label{sec-6}

\begin{itemize}

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

\item Creating a list

\begin{verbatim}

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

\end{verbatim}

\item Creating an array

\begin{verbatim}

     In []: a3 = array(l1)

\end{verbatim}

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 1}

\label{sec-7}

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

\end{frame}

\begin{frame}[fragile]

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

\label{sec-8}

\begin{itemize}

\item \texttt{.shape}

    To find the shape of the array

\begin{verbatim}

     In []: a1.shape

\end{verbatim}

\item \texttt{.shape}

    returns a tuple of shape

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 2}

\label{sec-9}

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

\end{frame}

\begin{frame}[fragile]

\frametitle{Homogeneous data}

\label{sec-10}

\begin{itemize}

\item All elements in array should be of same type

\begin{verbatim}

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

\end{verbatim}

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Implicit type casting}

\label{sec-11}

\begin{verbatim}

    In []: a4

\end{verbatim}

    All elements are type casted to string type

\end{frame}

\begin{frame}

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

\label{sec-12}

\begin{itemize}

\item \texttt{identity(n)}

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

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

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

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Learning exercise}

\label{sec-13}

\begin{itemize}

\item Find out about

\begin{itemize}

\item \texttt{zeros\_like()}

\item \texttt{ones()}

\item \texttt{ones\_like()}

\end{itemize}

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Array operations}

\label{sec-14}

\begin{itemize}

\item \texttt{a1 * 2}

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

\begin{itemize}

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

\end{itemize}

\item \texttt{a1 + 2}

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

\item \texttt{a1 += 2}

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

\begin{itemize}

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

\end{itemize}

\item \texttt{a1 + a2}

    does elements-wise addition.

\begin{itemize}

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

\end{itemize}

\item \texttt{a1 * a2}

    does element-wise multiplication

\end{itemize}

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

\end{frame}

\begin{frame}

\frametitle{Summary}

\label{sec-15}

  In this tutorial we covered,

\begin{itemize}

\item Basics of arrays

\item Creating arrays

\item Arrays from lists

\item Basic array operations

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Thank you!}

\label{sec-16}

  \begin{block}{}

  \begin{center}

  This spoken tutorial has been produced by the

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

  \end{center}

  \begin{center}

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

      Information \& Communication Technology \\ 

      MHRD, Govt. of India}.

  \end{center}  

  \end{block}

\end{frame}

\end{document}