.. Objectives

.. ----------

.. By the end of this tutorial you will --

.. 1. Get to know simple statistics functions like mean,std etc .. (Remembering)

.. #. Apply them on a real world example. (Applying)

.. Prerequisites

.. -------------

.. Getting started with IPython

.. Loading Data from files

.. Getting started with Lists

.. Author              : Puneeth 

   Internal Reviewer   : Anoop Jacob Thomas<anoop@fossee.in>

   External Reviewer   :

   Checklist OK?       : <put date stamp here, if OK> [2010-10-05]

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In this tutorial, we shall learn

 * Doing simple statistical operations in Python  

 * Applying these to real world problems 

We have a list of ages of a random group of people ::

       mean(age_list)

     two_dimension=[[1,5,6,8],[1,3,4,5]]

    mean(two_dimension)

    flattened_seq=[1,5,6,8,1,3,4,5]

    mean(flattened_seq)

   array([ 1. ,  4. ,  5. ,  6.5])

we pass an extra argument 0 in that case.

   array([ 5.  ,  3.25])

We can see more option of mean using ::

   mean?

Similarly we can calculate median and stanard deviation of a list

using the functions median and std::

      median(age_list)

      std(age_list)

Now lets apply this to a real world example 

We can do ::

   cat /home/fossee/sslc2.txt

to check the contents of the file.

Each line in the file is a set of 11 fields separated 

by semi-colons Consider a sample line from this file.  

A;015163;JOSEPH RAJ S;083;042;47;00;72;244;;; 

The following are the fields in any given line.

* Region Code which is 'A'

* Roll Number 015163

* Name JOSEPH RAJ S

* Marks of 5 subjects: ** English 083 ** Hindi 042 ** Maths 47 **

Science 35 ** Social 72

* Total marks 244

Now lets try and find the mean of English marks of all students.

For this we do. ::

     L=loadtxt('/home/fossee/sslc2.txt',usecols=(3,),delimiter=';')

     L

     mean(L)

loadtxt function loads data from an external file.Delimiter specifies

the kind of character are the fields of data seperated by. 

usecols specifies  the columns to be used so (3,). The 'comma' is added

because usecols is a sequence.

To get the median marks. ::

Standard deviation. ::

Now lets try and and get the mean for all the subjects ::

     L=loadtxt('/home/fossee/sslc2.txt',usecols=(3,4,5,6,7),delimiter=';')

     mean(L,0)

     array([ 73.55452504,  53.79828941,  62.83342759,  50.69806158,  63.17056881])

As we can see from the result mean(L,0). The resultant sequence  

is the mean marks of all students that gave the exam for the five subjects.

and ::

    mean(L,1)

is the average accumalative marks of individual students. Clearly, mean(L,0)

was a row wise calcultaion while mean(L,1) was a column wise calculation.

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This brings us to the end of the tutorial.

we have learnt

 * How to do the standard statistical operations sum , mean

   median and standard deviation in Python.

 * Combine text loading and the statistical operation to solve

   real world problems.

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This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India

Hope you have enjoyed and found it useful.