# HG changeset patch
# User shantanu <shantanu@fossee.in>
# Date 1269943844 -19800
# Node ID 093edb39f292e733bf1ae512b0085b67252479d6
# Parent  008c0edc6eac045aadacd99dae911ac81e6cf074
Added more changes to plotting-files script.

diff -r 008c0edc6eac -r 093edb39f292 plotting-files.txt
--- a/plotting-files.txt	Tue Mar 30 14:53:58 2010 +0530
+++ b/plotting-files.txt	Tue Mar 30 15:40:44 2010 +0530
@@ -5,13 +5,10 @@
 variables. Please make sure you have pendulum.txt file, we will
 be using it for introduction of concepts(requirements page!).
 
-In general, we don't plot (analytical) functions. We often have
-experimental data points, that we wish to plot. We shall look at
-inputting this data and plotting it. 
+We shall look at inputting experimental data and plotting it. 
 
-The data could be input (or entered) in two formats. For smaller data
-sets we could use lists to input the data and use plain text files for
-(somewhat?) larger ones. (Binary files?)
+The data could be input either as lists or read from plain text/
+binary files
 
 # Before starting with this video, you should be comfortable with
 #   - Lists
@@ -26,7 +23,7 @@
 Let's begin with inputting the data as lists and plotting it. 
 
 x = [0, 1, 2.1, 3.1, 4.2, 5.2]
-here x is a list. I python list is a container that holds number of
+here x is a list. In python list is a container that holds number of
 objects. Various functions related to lists will be covered in more 
 detail later.
 
@@ -45,8 +42,7 @@
 plot it, as we already did. 
 
 As an example we will use the data collected from a simple pendulum
-experiment. We have the data of, the length of pendulum vs. the time
-period of the pendulum in the file pendulum.txt
+experiment. 
 
 In []: cat pendulum.txt (windows?)
 
@@ -60,42 +56,60 @@
 and square of the time-period. 
 
 l = []
-#len? (confusion over 1 and l(damm they are really same looking:P))
 t = []
 tsq = []
 
 Now we open the file and read it line by line. 
 for line in open('pendulum.txt'):
 
+':' in end of for statement marks the start of block.
+
 open returns a iterable object which we traverse using for loop. In 
-python  iterates over items of any sequence.
+python for iterates over items of any sequence.
 #we will cover more of 'for' loop in later sections
 line is a string variable storing one line at a time as for loop 
 iterates through file.
-We split each line at the space 
+
+We split each line at the space using
+
     point = line.split()
 
-mind the indentation here.
+split function will return list. In this case it will have two 
+elements, first is length and second being time.
+
+mind the indentation here. Everything inside 'for' loop has to be 
+indented by 4 spaces.
 
 Then we append the length and time values to the corresponding
 lists. Note that they are converted from strings to floats, before
 appending to the lists
-    l.append(float(point[0])
-    t.append(float(point[1])
-We also calculate the squares of the time-period and append to the end
-of the tsq list. 
-    tsq.append(t[-1]*t[-1])
-For any given list to access last element python provides '-1' index, 
-so we use t[-1].
+    l.append(float(point[0]))
+append is function to append one element to the list.
+    t.append(float(point[1]))
+
+By this time we have time and length values in two lists. Now to get
+square of time values we will write one more for loop which this time
+iterate through list 't'
+
+for time in t:
+    tsq.append(time*time)
 
-Now the lists l, t have the required data. We can simply plot them, as
-we did already. 
+# We also calculate the squares of the time-period and append to the 
+# end of the tsq list. 
+#     tsq.append(t[-1]*t[-1])
+# For any given list to access last element python provides '-1' 
+# index, so we use t[-1].
 
-plot(l, t, 'o')
+Now lists l(en) and tsq have the required data. We can simply plot 
+them, as we did already.
 
-Enjoy!
+plot(l, tsq, 'o')
 
+Enjoy(Thank you)!
+
+For alternate ways of loading data from files go through tutorial on 
+loadtxt
 ******************
-We should have two tutorials here, one should be basic, using for loops
-and lists
+We should have two tutorials here, one should be basic, using for 
+loops and lists
 Second one using loadtxt.