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%Tutorial slides on Python.

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% Author: FOSSEE

% Copyright (c) 2009, FOSSEE, IIT Bombay

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% Title page

\title[Plotting with Python]{Python for Science and Engg: Plotting experimental data}

\author[FOSSEE] {FOSSEE}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}

\date[] {31, October 2009\\Day 1, Session 2}

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    \frametitle{Outline}

    \tableofcontents[currentsection,currentsubsection]

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    \frametitle{Outline}

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% DOCUMENT STARTS

\begin{document}

\begin{frame}

  \titlepage

\end{frame}

\begin{frame}

  \frametitle{Outline}

  \tableofcontents

  % You might wish to add the option [pausesections]

\end{frame}

\begin{frame}

\frametitle{Why we didn't close the IPython??}

\begin{itemize}

  \item IPython provides a convenient feature

  \item To go back, edit, and re-run commands

  \item But when you close, this is lost

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{But its impractical..}

\begin{itemize}

  \item We can't keep running IPython for days

  \item And its a pain to go back and edit

\end{itemize}

And the solution is..\\

\begin{center}

\alert {\typ{Scripts!!}}

\end{center}

\end{frame}

\section{Scripts}

\begin{frame}[fragile]

\frametitle{Python Scripts}

\begin{itemize}

\item Put all commands used in review problem into a file. 

\item use hist command of IPython.

\end{itemize}

\begin{lstlisting}

  In []: %hist

  In []: %hist -n

\end{lstlisting}

\end{frame}

\begin{frame}

\frametitle{Python Scripts\ldots}

  \begin{itemize}

    \item Open a new file in an \alert{editor}

    \item Copy and paste required lines from the output of \typ{\%hist -n}

    \item Save the file as \typ{sine_plot.py}

  \end{itemize}

  \begin{itemize}

  \item run the file in IPython using \typ{\%run sine_plot.py}\\

  \end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Why would I plot f(x)?}

How often do we plot analytical functions?\\We plot experimental data more.

\begin{lstlisting}

In []: x = [0, 1, 2, 3]

In []: y = [7, 11, 15, 19]

In []: plot(x, y)

Out[]: [<matplotlib.lines.Line2D object at 0xa73aa8c>]

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\begin{figure}

\includegraphics[width=3.5in]{data/straightline.png}

\end{figure}

\alert{Is this what you have??}

\end{frame}

\begin{frame}[fragile]

\frametitle{Plotting points}

\begin{itemize}

\item What if we want to plot the points!

\end{itemize}

\begin{lstlisting}

  In []: clf()

  In []: plot(L, TSq, 'o')

  Out[]: [<matplotlib.lines.Line2D object at 0xac17e0c>]

  In []: clf()

  In []: plot(L, TSq, '.')

  Out[]: [<matplotlib.lines.Line2D object at 0xac17e0c>]

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\begin{figure}

\includegraphics[width=2in]{data/stline_dots.png}

\includegraphics[width=2in]{data/stline_points.png}

\end{figure}

\end{frame}

\begin{frame}[fragile]

\frametitle{Additional Plotting Attributes}

\begin{itemize}

  \item \kwrd{'o'} - Dots

  \item \kwrd{'.'} - Smaller Dots

  \item \kwrd{'-'} - Lines

  \item \kwrd{'- -'} - Dashed lines

\end{itemize}

\end{frame}

\section{Lists}

\begin{frame}[fragile]

  \frametitle{How to create the data?}

What were \typ{x} and \typ{y}??\\

\begin{center}

\alert{\typ{lists!!}}

\end{center}

\begin{lstlisting}

In []: mtlist = [] #Empty List

In []: lst = [1,2,3,4,5] 

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\frametitle{Accessing elements of a list}

\begin{lstlisting}

In []: lst[0]+lst[1]+lst[-1]

Out[]: 8

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{List: Slicing}

  \begin{block}{Remember\ldots}

	\kwrd{In []: lst = [1,2,3,4,5]}

  \end{block}

\alert{\typ{list[initial:final:step]}}

\begin{lstlisting}

In []: lst[1:3]  # A slice.

Out[]: [2, 3]

In []: lst[1:-1]

Out[]: [2, 3]

\end{lstlisting}

\end{frame}

%% more on list slicing

\begin{frame}[fragile]

\frametitle{List operations}

\begin{lstlisting}

In []: anthrlst = [6,7,8,9]

In []: lnglst = lst + anthrlst

In []: lnglst

Out[]: [1, 2, 3, 4, 5, 6, 7, 8, 9]

In []: lst.append(6)

In []: lst

Out[]: [1, 2, 3, 4, 5, 6]

\end{lstlisting}

%\inctime{10}

\end{frame}

\section{Simple Pendulum}

\begin{frame}[fragile]

\frametitle{Simple Pendulum - L and T}

Let us look at the example of the Simple Pendulum experiment.

\begin{center}

\begin{small}

\begin{tabular}{| c | c | c |}

\hline

$L$ & $T$ & $T^2$ \\ \hline

0.1 & 0.6900 & \\ \hline

0.2 & 0.8989 & \\ \hline

0.3 & 1.1867 & \\ \hline

0.4 & 1.2991 & \\ \hline

0.5 & 1.4656 & \\ \hline

0.6 & 1.5843 & \\ \hline

0.7 & 1.7706 & \\ \hline

0.8 & 1.8296 & \\ \hline

0.9 & 1.9440 & \\ \hline

\end{tabular}

\end{small}\\

\alert{$L \alpha T^2$}

\end{center}

\end{frame}

\begin{frame}[fragile]

\frametitle{Lets use lists}

\begin{lstlisting}

In []: L = [0.1, 0.2, 0.3, 0.4, 0.5, 

            0.6, 0.7, 0.8, 0.9]

In []: T = [0.69, 0.8989, 1.1867, 

            1.2991, 1.4656, 1.5843, 

            1.7706, 1.8296, 1.9440]

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\frametitle{Plotting $L$ vs $T^2$}

\begin{itemize}

\item We must square each of the values in T

\item How to do it?

\item We use a \kwrd{for} loop to iterate over T

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Plotting $L$ vs $T^2$}

\begin{lstlisting}

In []: TSq = []

In []: for t in T:

 ....:     TSq.append(t*t)

In []: plot(L, TSq)

Out[]: [<matplotlib.lines.Line2D object at 0xa5b05ac>]

\end{lstlisting}

This gives the list \kwrd{TSq} which is the list of squares of T values.

\end{frame}

\begin{frame}[fragile]

\begin{figure}

\includegraphics[width=3.5in]{data/L-TSq-limited.png}

\end{figure}

\end{frame}

\begin{frame}[fragile]

\frametitle{More of \texttt{for}}

\begin{itemize}

\item Used to iterate over lists

\item Let us look at another example.

\end{itemize}

\begin{lstlisting}

In []: lst = [1,2,3,4,5,6]

In []: for num in lst:

 ....:     print num, num*num

 ....:    

1 1

2 4

3 9

4 16

5 25

6 36

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\frametitle{What about larger data sets??}

\alert{Data is usually present in a file!} \\

Lets look at the pendulum.txt file.

\begin{lstlisting}

$cat data/pendulum.txt 

1.0000e-01 6.9004e-01

1.1000e-01 6.9497e-01

1.2000e-01 7.4252e-01

1.3000e-01 7.5360e-01

1.4000e-01 8.3568e-01

1.5000e-01 8.6789e-01

\end{lstlisting}

\ldots

\end{frame}

\begin{frame}[fragile]

\frametitle{Reading pendulum.txt}

\begin{itemize}

  \item We now wish to repeat the plot using the values from a file

  \item Given a file containing L vs. T values 

  \item Column1 - L; Column2 - T  

  \item Read the file

  \item Plot points for L vs. $T^2$ 

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Reading pendulum.txt}

\begin{lstlisting}

In []: L = []

In []: T = []

In []: for line in open('pendulum.txt'):

  ....     points = line.split()

  ....     L.append(float(points[0]))

  ....     T.append(float(points[1]))

\end{lstlisting}

\begin{itemize}

\item We now have two lists L and T

\item Now, Repeat previous steps for plotting

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Plotting from pendulum.txt}

\begin{lstlisting}

In []: TSq = []

In []: for t in T:

 ....:     TSq.append(t*t)

In []: plot(L, TSq, '.')

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\begin{figure}

\includegraphics[width=3.5in]{data/L-Tsq.png}

\end{figure}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Reading files \ldots}

\typ{In []: for line in open('pendulum.txt'):}

\begin{itemize}

\item opening file `pendulum.txt'

\item iterating through the file by reading each line into variable \typ{line}

\item \typ{line} is a \kwrd{string} variable

\end{itemize}

\end{frame}

\section{Strings}

\begin{frame}[fragile]

\frametitle{Strings}

Anything within ``quotes'' is a string!

\begin{lstlisting}

' This is a string '  

" This too! "

""" This one too! """

''' And one more! '''

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\frametitle{Strings and \typ{split()}}

  \begin{lstlisting}

In []: line = 'hello world'

In []: line.split()

Out[]: ['hello', 'world']

  \end{lstlisting}

This is what happens with \typ{line}

  \begin{lstlisting}

In []: line = '1.2000e-01 7.4252e-01'

In []: line.split()

Out[]: ['1.2000e-01', '7.4252e-01']

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

\frametitle{Getting floats from strings}

  \begin{lstlisting}

In []: type(points[0])

Out[]: <type 'str'>

  \end{lstlisting}

But, we need floating point numbers

  \begin{lstlisting}

In []: t = float(point[0])

In []: type(t)

Out[]: <type 'float'>

  \end{lstlisting}

\end{frame}

\section {Summary}

\begin{frame}

\frametitle{Summary}

So what did we learn in this session??

\begin{itemize}

  \item Creating and running Python scripts

  \item Plotting points and Plotting attributes

  \item Lists

  \item \kwrd{for}

  \item Reading files

  \item Strings

\end{itemize}

\end{frame}

\end{document}