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.. Objectives
.. ----------
.. By the end of this tutorial, you will be able to
.. 1. Defining a list of numbers
.. 2. Squaring a list of numbers
.. 3. Plotting data points.
.. 4. Plotting errorbars.
.. Prerequisites
.. -------------
.. 1. getting started with plotting
.. Author : Amit
Internal Reviewer : Anoop Jacob Thomas<anoop@fossee.in>
External Reviewer :
Checklist OK? : <put date stamp here, if OK> [2010-10-05]
.. #[[Anoop: Add quickref]]
.. #[[Anoop: Slides are incomplete, add summary slide, thank you slide
etc.]]
===============================
Plotting Experimental Data
===============================
{{{ Show the slide containing title }}}
Hello and welcome to this tutorial on Plotting Experimental data,
presented by the fossee team.
{{{ Show the Outline Slide }}}
.. #[[Anoop: outline slide is missing]]
One needs to be familiar with the concepts of plotting
mathematical functions in Python.
We will use data from a Simple Pendulum Experiment to illustrate.
.. #[[Anoop: what do you mean by points here? if you mean the
points/numbered list in outline slide, then remove the usage point
from here.]]
{{{ Simple Pendulum data Slide }}}
.. #[[Anoop: slides are incomplete, work on slides and context
switches]]
As we know for a simple pendulum length,L is directly proportional to
the square of time,T. We shall be plotting L and T^2 values.
First we will have to initiate L and T values. We initiate them as sequence
of values. We define a sequence by comma seperated values inside two square brackets.
This is also called List.Lets create two sequences L and t.
.. #[[Anoop: instead of saying "to tell ipython a sequence of values"
and make it complicated, we can tell, we define a sequence as]]
.. #[[Anoop: sentence is incomplete, can be removed]]
{{{ Show the initializing L&T slide }}}
Type in ipython shell ::
L = [0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9]
t= [0.69, 0.90, 1.19,1.30, 1.47, 1.58, 1.77, 1.83, 1.94]
To obtain the square of sequence t we will use the function square
with argument t.This is saved into the variable tsquare.::
tsquare=square(t)
tsqaure
array([ 0.4761, 0.81 , 1.4161, 1.69 , 2.1609, 2.4964, 3.1329,
3.3489, 3.7636])
.. #[[Anoop: how do you get the array([ 0.4761 ....]) output?]]
Now to plot L vs T^2 we will simply type ::
plot(L,tsquare,'.')
.. #[[Anoop: be consistent with the spacing and all.]]
'.' here represents to plot use small dots for the point. ::
clf()
This clears the plot.
You can also specify 'o' for big dots.::
plot(L,tsquare,'o')
clf()
Pause video here and solve this exercise. Resume the video once done.
%% %% Plot the given experimental data with large dots.The data is
on your screen.
%% %% Plot the given experimental data with small dots.
The data is on your screen
.. #[[Anoop: Make sure code is correct, corrected plot(L,t,o) to
plot(L,t,'o')]]
.. #[[Anoop: again slides are incomplete.]]
For any experimental there is always an error in measurements due to
instrumental and human constaraints.Now we shall try and take into
account error into our plots . The Error values for L and T are on
your screen.We shall again intialize the sequence values in the same
manner as we did for L and t
The error data we will use is on your screen.
{{{ Show the Adding Error Slide }}}
.. #[[Anoop: give introduction to error and say what we are going to
do]]
::
delta_L= [0.08,0.09,0.07,0.05,0.06,0.00,0.06,0.06,0.01]
delta_T= [0.04,0.08,0.03,0.05,0.03,0.03,0.04,0.07,0.08]
Now to plot L vs T^2 with an error bar we use the function errorbar()
The syntax of the command is as given on the screen. ::
errorbar(L,tsquare,xerr=delta_L, yerr=delta_T, fmt='b.')
This gives a plot with error bar for x and y axis. The dots are of
blue color. The parameters xerr and yerr are error on x and y axis and
fmt is the format of the plot.
similarly we can draw the same error bar with big red dots just change
the parameters to fmt to 'ro'. ::
clf()
errorbar(L,tsquare,xerr=delta_L, yerr=delta_T, fmt='ro')
thats it. you can explore other options to errorbar using the documentation
of errorbar.::
errorbar?
Please, pause the video here. Do the exercises and then continue.
%% %% Plot the given experimental data with large green dots.Also include
the error in your plot.
Please, pause the video here. Do the exercise and then continue.
{{{ Show Summary Slide }}}
In this tutorial we have learnt :
1. How to declare a sequence of numbers.
2. Plotting experimental data.
#. The various options available for plotting dots instead of lines.
#. Plotting experimental data such that we can also represent error.
{{{ Show the "sponsored by FOSSEE" slide }}}
.. #[[Anoop: again slides are incomplete]]
This tutorial was created as a part of FOSSEE project.
Hope you have enjoyed and found it useful.
Thank You!
|
