Changed session-2 - now uses loadtxt.

--HG--
branch : scipyin2010

4 files changed, 96 insertions, 225 deletions

diff --git a/day1/data/stline_dots.png b/day1/data/stline_dots.png
index ff6ec70..015dfec 100644
--- a/day1/data/stline_dots.png
+++ b/day1/data/stline_dots.png
diff --git a/day1/data/stline_points.png b/day1/data/stline_points.png
index 9e3f198..885f7f5 100644
--- a/day1/data/stline_points.png
+++ b/day1/data/stline_points.png
diff --git a/day1/data/straightline.png b/day1/data/straightline.png
index b963f55..a7ad2d2 100644
--- a/day1/data/straightline.png
+++ b/day1/data/straightline.png
diff --git a/day1/session2.tex b/day1/session2.tex
index 75ce2c5..e63b3be 100644
--- a/day1/session2.tex
+++ b/day1/session2.tex
@@ -78,7 +78,7 @@
 \author[FOSSEE group] {FOSSEE}
 
 \institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
-\date[] {SciPy 2010, Introductory tutorials,\\Day 1, Session 2}
+\date[] {SciPy.in 2010, Tutorials}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 %\pgfdeclareimage[height=0.75cm]{iitmlogo}{iitmlogo}
@@ -133,7 +133,7 @@ In []: time = [0, 1, 2, 3]
 
 In []: distance = [7, 11, 15, 19]
 
-In []: plot(time,distance)
+In []: plot(time, distance)
 Out[]: [<matplotlib.lines.Line2D object at 0xa73aa8c>]
 
 In []: xlabel('time')
@@ -219,50 +219,16 @@ Out[]: 12
 \end{frame}
 
 \begin{frame}[fragile]
-  \frametitle{List: Slicing}
-  \begin{block}{Remember\ldots}
-	\kwrd{In []: p = [ 2, 3, 5, 7]}
-  \end{block}
+\frametitle{List: Appending elements}
 \begin{lstlisting}
-In []: p[1:3]
-Out[]: [3, 5]
-\end{lstlisting}
-\emphbar{A slice}
-\begin{lstlisting}
-In []: p[0:-1]
-Out[]: [2, 3, 5]
-In []: p[::2]
-Out[]: [2, 5]
-\end{lstlisting}
-\alert{\typ{list[initial:final:step]}}
-\end{frame}
-
-\begin{frame}[fragile]
-  \frametitle{List: Slicing}
-  What is the output of the following?
-\begin{lstlisting}
-In []: p[1::2]
-
-In []: p[1:-1:2]
-\end{lstlisting}
-\end{frame}
-
-
-%% more on list slicing
-\begin{frame}[fragile]
-\frametitle{List operations}
-\begin{lstlisting}
-In []: b = [ 11, 13, 17]
-In []: c = p + b
-
-In []: c
-Out[]: [2, 3, 5, 7, 11, 13, 17]
-
 In []: p.append(11)
 In []: p
 Out[]: [ 2, 3, 5, 7, 11]
+
+In []: b = [11, 13, 17]
+In []: p.append(b)
+Out[]: [ 2, 3, 5, 7, 11, [11, 13, 17]]
 \end{lstlisting}
-Question: Does \typ{c} change now that \typ{p} is changed?
 %\inctime{10}
 \end{frame}
 
@@ -288,95 +254,7 @@ $L$ & $T$ & $T^2$ \\ \hline
 \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, 0.90, 1.19, 
-            1.30, 1.47, 1.58, 
-            1.77, 1.83, 1.94]
-\end{lstlisting}
-\alert{Gotcha}: Make sure \typ{L} and \typ{t} have the same number
-of elements
-
-\begin{lstlisting}
-In []: print len(L), len(t)
-\end{lstlisting}
-
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{Plotting $L$ vs $T^2$}
-\begin{itemize}
-\item We must square each of the values in \typ{t}
-\item How do we do it?
-\item We use a \kwrd{for} loop to iterate over \typ{t}
-\end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{Plotting $L$ vs $T^2$}
-\begin{lstlisting}
-In []: tsq = []
-
-In []: for time in t:
- ....:     tsq.append(time*time)
- ....:
- ....:
-
-\end{lstlisting}
-This gives \typ{tsq} which is the list of squares of \typ{t} values.
-\begin{lstlisting}
-In []: print len(L), len(t), len(tsq)
-Out[]: 9 9 9
-\end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
-  \frametitle{How do you exit the \texttt{for} loop?}
-  Hitting the ``ENTER'' key twice returns the cursor to the previous indentation level
-  \begin{lstlisting}
-    In []: for time in t:
-     ....:     tsq.append(time*time)
-     ....:     
-     ....:     
-
-    In []: plot(L, tsq)
-  \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
-\begin{figure}
-\includegraphics[width=3.5in]{data/L-TSq-limited.png}
-\end{figure}
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{What about larger data sets?}
-\alert{Data is usually present in a file!} \\
-Lets look at the \typ{pendulum.txt} file.
-\begin{lstlisting} 
-In []: cat 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
-\end{lstlisting}  %$
-\ldots
-\end{frame}
-
-\begin{frame}[fragile]
-\frametitle{Reading \typ{pendulum.txt}}
-\begin{itemize}
-  \item File contains L vs.\ T values 
-  \item First Column - L values
-  \item Second Column - T values
-  \item Let us generate a plot from the data file
-\end{itemize}
+Our data is present in \typ{pendulum.txt}. Let's look at it.
 \end{frame}
 
 \begin{frame}[fragile]
@@ -398,132 +276,127 @@ In []: ?
     \end{lstlisting}
 \end{frame}
 
-
 \begin{frame}[fragile]
-\frametitle{Plotting from \typ{pendulum.txt}}
-Open a new script and save as \typ{pendulum_plot.py}
-\begin{lstlisting}
-L = []
-t = []
-for line in open('pendulum.txt'):
-    point = line.split()
-    L.append(float(point[0]))
-    t.append(float(point[1]))
-tsq = []
-for time in t:
-    tsq.append(time*time)
-plot(L, tsq, '.')
-\end{lstlisting}
-\end{frame}
-
-\begin{frame}
-\frametitle{Save and run}
+\frametitle{Looking at \typ{pendulum.txt}}
+\begin{lstlisting} 
+In []: cat 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
+\end{lstlisting}  %$
+\ldots
 \begin{itemize}
-    \item Save as \typ{pendulum\_plot.py}
-  \item Run using \kwrd{\%run -i pendulum\_plot.py}
+  \item File contains L vs.\ T values 
+  \item First Column -- L values
+  \item Second Column -- T values
 \end{itemize}
 \end{frame}
 
 \begin{frame}[fragile]
-\begin{figure}
-\includegraphics[width=3.5in]{data/L-Tsq.png}
-\end{figure}
+  \frametitle{\typ{loadtxt}}
+  \begin{itemize}
+  \item We shall use the \typ{loadtxt} command to load data
+  \item Let's use \typ{primes.txt} file learn to use it
+  \item \typ{primes.txt} has a single column
+  \item Then, we shall use it for \typ{pendulum.txt} -- 2 cols
+  \end{itemize}
 \end{frame}
 
 \begin{frame}[fragile]
-  \frametitle{Reading files \ldots}
-\typ{for line in open('pendulum.txt'):}
-\begin{itemize}
-\item opening file `\typ{pendulum.txt}'
-\item reading the file line by line
-\item \typ{line} is a \kwrd{string}
-\end{itemize}
+\frametitle{What's in \typ{primes.txt}?}
+Lets look at the \typ{primes.txt} file.
+\begin{lstlisting} 
+In []: cat primes.txt 
+2
+3      
+5      
+7     
+11     
+13
+.
+.
+.
+\end{lstlisting}  %$
 \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}
-Why so many?
-\begin{lstlisting}
-' "Do or do not.  No try." said Yoda.'  
-" ' is a mighty lonely quote."
-\end{lstlisting}
-The triple quoted ones can span multiple lines!
+  \frametitle{\typ{loadtxt} \ldots}
+  \begin{lstlisting}
+In []: primes = loadtxt('primes.txt')
+In []: primes
+Out[]: array([ 2., 3., 5., 7., 11., 13., 
+               17., 19., 23., 29., 31., 
+               37., 41., 43., 47., 53., 
+               59., 61., 67., 71., 73., 
+               79., 83., 89., 97.])
+  \end{lstlisting}
 
-\begin{lstlisting}
-""" The quick brown
-fox jumped over
-    the lazy dingbat. 
-"""
-\end{lstlisting}
 \end{frame}
 
 \begin{frame}[fragile]
-\frametitle{Strings and \typ{split()}}
+  \frametitle{Reading \typ{pendulum.txt}}
   \begin{lstlisting}
-In []: greet = 'hello world'
-
-In []: greet.split()
-Out[]: ['hello', 'world']
+In []: pend = loadtxt('pendulum.txt')
+In []: pend
   \end{lstlisting}
-This is what happens with \typ{line}
-  \begin{lstlisting}
-In []: line = '1.20 7.42'
-
-In []: point = line.split()
+  \begin{itemize}
+  \item \typ{pend} is 2 Dimensional. 
+  \item We don't \alert{yet} know how to handle it.
+  \item We obtain 1D sequences using \typ{unpack=True}
+  \end{itemize}
 
-In []: point
-Out[]: ['1.20', '7.42']
+  \begin{lstlisting}
+In []: L, T = loadtxt('pendulum.txt', 
+                      unpack=True)
+In []: print L, T
+In []: print len(L), len(T)
+Out[]: 90 90
   \end{lstlisting}
 \end{frame}
 
 \begin{frame}[fragile]
-\frametitle{Getting floats from strings}
-  \begin{lstlisting}
-In []: type(point[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}
+\frametitle{Plotting $L$ vs $T^2$}
+\begin{itemize}
+\item We must square each of the values in \typ{T}
+\item How to do it?
+\item We use a \kwrd{for} loop to iterate over \typ{T}
+\end{itemize}
 \end{frame}
 
 \begin{frame}[fragile]
-\frametitle{Let's review the code}
+\frametitle{Plotting $L$ vs $T^2$}
 \begin{lstlisting}
-L = []
-t = []
-for line in open('pendulum.txt'):
-    point = line.split()
-    L.append(float(point[0]))
-    t.append(float(point[1]))
-tsq = []
-for time in t:
-    tsq.append(time*time)
-plot(L, tsq, '.')
+In []: tsq = []
+
+In []: for time in T:
+ ....:     tsq.append(time*time)
+ ....:
+ ....:
+
 \end{lstlisting}
+\alert{Hit ``ENTER'' key twice, to get out of \typ{for} loop}.
+
+\begin{lstlisting}
+In []: print len(tsq)
+Out[]: 90
+\end{lstlisting}
+\typ{tsq} is a \kwrd{list} of squares of \typ{T} values.
 \end{frame}
 
+
 \begin{frame}[fragile]
+\frametitle{Plotting $L$ vs $T^2$ \ldots}
+
+\begin{lstlisting}
+In []: plot(L, tsq, '.')
+\end{lstlisting}
+
 \begin{figure}
-\includegraphics[width=3.5in]{data/L-Tsq.png}
+  \includegraphics[width=3.5in]{data/L-Tsq.png}
 \end{figure}
+
 \end{frame}
 
 \section {Summary}
@@ -533,9 +406,7 @@ plot(L, tsq, '.')
   \item Plot attributes and plotting points
   \item Lists
   \item \kwrd{for}
-  \item Reading files
-  \item Tokenizing
-  \item Strings
+  \item Loading data from files
 \end{itemize}
 \end{frame}