1. Python for Science and Engg:
Interactive Plotting
FOSSEE
Department of Aerospace Engineering
IIT Bombay
12 February, 2010
Day 1, Session 1
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2. Workshop Schedule: Day 1
Session 1 Fri 14:00–15:00
Session 2 Fri 15:05–16:05
Session 3 Fri 16:10–17:10
Quiz 1 Fri 17:10–17:25
Exercises Thu 17:30–18:00
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3. Workshop Schedule: Day 2
Session 1 Sat 09:00–10:00
Session 2 Sat 10:05–11:05
Session 3 Sat 11:20–12:20
Quiz 2 Fri 14:25–14:40
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4. Workshop Schedule: Day 3
Session 1 Sun 09:00–10:00
Session 2 Sun 10:05–11:05
Session 3 Sun 11:20–12:20
Quiz 3 Sun 12:20–12:30
Exercises Sun 12:30–13:00
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5. Checklist
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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6. Checklist
Checklist
1
IPython
2
Editor
3
Data files:
sslc1.txt
pendulum.txt
points.txt
pos.txt
holmes.txt
4
Python scripts:
sslc_allreg.py
sslc_science.py
5
Images
lena.png
smoothing.gif
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7. Checklist
About the Workshop
Intended Audience
Engg., Mathematics and Science teachers.
Interested students from similar streams.
Goal: Successful participants will be able to
Use Python as plotting, computational tool.
Understand how to use Python as a scripting and
problem solving language.
Train students for the same.
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8. Starting up Ipython
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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9. Starting up Ipython
Starting up . . .
$ ipython -pylab
In []: print "Hello, World!"
Hello, World!
Exiting
In []: ^D(Ctrl-D)
Do you really want to exit([y]/n)? y
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10. Loops
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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11. Loops
Loops
Breaking out of loops
In []: while True:
...: print "Hello, World!"
...:
Hello, World!
Hello, World!^C(Ctrl-C)
------------------------------------
KeyboardInterrupt
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12. Plotting
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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13. Plotting Drawing plots
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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14. Plotting Drawing plots
First Plot
In []: x = linspace(0, 2*pi, 50)
In []: plot(x, sin(x))
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15. Plotting Drawing plots
Walkthrough
x = linspace(start, stop, num)
returns num evenly spaced points, in the interval
[start, stop].
x[0] = start
x[num - 1] = end
plot(x, y)
plots x and y using default line style and color
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16. Plotting Decoration
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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17. Plotting Decoration
Adding Labels
In []: xlabel(’x’)
In []: ylabel(’sin(x)’)
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18. Plotting Decoration
Another example
In []: clf()
Clears the plot area.
In []: y = linspace(0, 2*pi, 50)
In []: plot(y, sin(2*y))
In []: xlabel(’y’)
In []: ylabel(’sin(2y)’)
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19. Plotting More decoration
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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20. Plotting More decoration
Title and Legends
In []: title(’Sinusoids’)
In []: legend([’sin(2y)’])
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21. Plotting More decoration
Legend Placement
In []: legend([’sin(2y)’], loc = ’center’)
’best’
’right’
’center’
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22. Plotting More decoration
Saving & Closing
In []: savefig(’sin.png’)
In []: close()
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23. Multiple plots
Outline
1 Checklist
2 Starting up Ipython
3 Loops
4 Plotting
Drawing plots
Decoration
More decoration
5 Multiple plots
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24. Multiple plots
Overlaid Plots
In []: clf()
In []: plot(y, sin(y))
In []: plot(y, cos(y))
In []: xlabel(’y’)
In []: ylabel(’f(y)’)
In []: legend([’sin(y)’, ’cos(y)’])
By default plots would be overlaid!
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25. Multiple plots
Plotting separate figures
In []: clf()
In []: figure(1)
In []: plot(y, sin(y))
In []: figure(2)
In []: plot(y, cos(y))
In []: savefig(’cosine.png’)
In []: figure(1)
In []: title(’sin(y)’)
In []: savefig(’sine.png’)
In []: close()
In []: close()
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26. Multiple plots
Showing it better
In []: plot(y, cos(y), ’r’)
In []: clf()
In []: plot(y, sin(y), ’g’, linewidth=2)
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27. Multiple plots
Annotating
In []: annotate(’local max’, xy=(1.5, 1))
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28. Multiple plots
Axes lengths
Get the axes limits
In []: xmin, xmax = xlim()
In []: ymin, ymax = ylim()
Set the axes limits
In []: xlim(xmin, 2*pi)
In []: ylim(ymin-0.2, ymax+0.2)
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29. Multiple plots
Review Problem
1
Plot x, -x, sin(x), xsin(x) in range −5π to 5π
2
Add a legend
3
Annotate the origin
4
Set axes limits to the range of x
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30. Multiple plots
Review Problem . . .
Plotting . . .
In []: x=linspace(-5*pi, 5*pi, 500)
In []: plot(x, x, ’b’)
In []: plot(x, -x, ’b’)
In []: plot(x, sin(x), ’g’, linewidth=2)
In []: plot(x, x*sin(x), ’r’,
linewidth=3)
.
.
.
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31. Multiple plots
Review Problem . . .
Legend & Annotation. . .
In []: legend([’x’, ’-x’, ’sin(x)’,
’xsin(x)’])
In []: annotate(’origin’, xy = (0, 0))
Setting Axes limits. . .
In []: xlim(-5*pi, 5*pi)
In []: ylim(-5*pi, 5*pi)
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32. Multiple plots
Saving Commands
Save commands of review problem into file
Use %hist command of IPython
Identify the required line numbers
Then, use %save command of IPython
In []: %hist
In []: %save four_plot.py 16 18-27
Careful about errors!
%hist will contain the errors as well,
so be careful while selecting line numbers.
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33. Multiple plots
Python Scripts. . .
This is called a Python Script.
run the script in IPython using
%run -i four_plot.py
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34. Multiple plots
What did we learn?
Starting up IPython
%hist - History of commands
%save - Saving commands
Running a script using %run -i
Creating simple plots.
Adding labels and legends.
Annotating plots.
Changing the looks: size, linewidth
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