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Very nice site!
== Project ==
Very nice site!
Learn how to plot data with the matplotlib plotting library. Ditch Excel forever!
Very nice site!
== Goals ==
== Project steps ==
* practice reading data from a file
* practice using the matplotlib Python plotting library to analyze data and generate graphs
=== 1. Create a basic plot ===
== Project setup ==
=== Install the project dependencies ===
Run <code>python basic_plot.py</code>. This will pop up a window with a dot plot of some data.
Open <code>basic_plot.py</code>. Read through the code in this file. The meat of the file is in one line:
<pre>pyplot.plot([0, 2, 4, 8, 16, 32], "o")</pre>
Please follow the official matplotlib installation instructions at http://matplotlib.sourceforge.net/users/installing.html
In this example, the first argument to <code>pyplot.plot</code> is the list of y values, and the second argument describes how to plot the data. If two lists had been supplied, <code>pyplot.plot</code> would consider the first list to be the x values and the second list to be the y values.
The dependencies vary across operating systems. http://matplotlib.sourceforge.net/users/installing.html#build-requirements summarizes what you'll need for your operating system.
<li>Change the plot to display lines between the data points by changing
<pre>pyplot.plot([0, 2, 4, 8, 16, 32], "o")</pre>
A universal dependency is the NumPy scientific computing library. NumPy has download and installation instructions at http://numpy.scipy.org/
Installing matplotlib and its dependencies is somewhat involved; please ask for help if you get stuck or don't know where to start!
<pre>pyplot.plot([0, 2, 4, 8, 16, 32], "o-")</pre>
==== Mac OS X users only ====
and re-run the script. What changed?
If you do not already have a C compiler installed, you'll need one to install matplotlib. You have several options depending on your situation:
# Download and install Xcode (1.5 GB) from https://developer.apple.com/xcode/
# Download and install Command Line Tools for Xcode (175 MB) from https://developer.apple.com/downloads/index.action. This requires an Apple Developer account (free, but you have to sign up).
Add x-values to the data by changing
# Download and install kennethreitz's gcc installer (requires 10.6 or 10.7) from https://github.com/kennethreitz/osx-gcc-installer/
<pre>pyplot.plot([0, 2, 4, 8, 16, 32], "o-")</pre>
Please wave over a staff member and we'll help you pick which option is best for you computer.
<pre>x_values = [0, 4, 7, 20, 22, 25]
=== Download and un-archive the Jeopardy database project skeleton code ===
y_values = [0, 2, 4, 8, 16, 32]
pyplot.plot(x_values, y_values, "o-")</pre>
and re-run the script. What changed?
* http://web.mit.edu/jesstess/www/IntermediatePythonWorkshop/JeopardyDatabase.zip
Note how matplotlib automatically resizes the graph to fit all of the points in the figure for you.
Un-archiving will produce a <code>JeopardyDatabase</code> folder containing 3 Python files and one SQL database dump.
Read about how to generate random integers on http://docs.python.org/library/random.html#random.randint.
Then, instead of hard-coding y values in <code>basic_plot.py</code>, generate a list of random y values and plot them.
=== Create a SQLite database from the database dump ===
An example plot using random y values might look like this:
Inside <code>JeopardyDatabase</code> is a file called <code>jeopardy.dump</code> which contains a SQL database dump. We need to turn that database dump into a SQLite database.
<br />
<b>Read these short documents</b>:
Once you have SQLite installed, you can create a database from jeopardy.dump with:
* Pyplot tutorial (just this one section; stop before the next section "Controlling line properties"): http://matplotlib.sourceforge.net/users/pyplot_tutorial.html#pyplot-tutorial
* List of line options, including line style and marker shapes and colors: http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.plot
<pre>sqlite3 jeopardy.db < jeopardy.dump</pre>
This creates a sqlite3 database called <code>jeopardy.db</code>
=== Test your setup ===
At a command prompt, start <code>sqlite3</code> using the <code>jeopardy.db</code> database by running:
<pre>sqlite3 jeopardy.db</pre>
That should start a sqlite prompt that looks like this:
SQLite version 3.6.12
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
At that sqlite prompt, type <code>.tables</code> and hit enter. That should display a list of the tables in this database:
<pre>sqlite> .tables
category clue
From a command prompt, navigate to the <code>JeopardyDatabase</code> directory and run
<pre>python jeopardy_categories.py</pre>
You should see a list of 10 jeopardy categories printed to the screen. If you don't, let a staff member know so you can debug this together.
== Project steps ==
=== 1. Look at the layout of the Jeopardy database ===
Start sqlite with <code>sqlite3 jeopardy.db</code>. Then look at the tables in your database by running the following commands and the sqlite prompt:
* <tt>.table</tt>, which will list the tables in the database
* <tt>.schema category</tt>, which will show the organization of the <tt>category</tt> table, including the fields and the data types they store.
It should look like this:
<pre>sqlite> .schema category
CREATE TABLE "category" (
boardPosition INTEGER
This tells us that the <code>category</code> table has 4 fields: <code>id</code>, <code>name</code>, <code>game</code>, and <code>boardPosition</code>.
* <tt>.schema clue</tt>
Read these short documents:
* What is SQL? http://www.w3schools.com/sql/sql_intro.asp
* What is a database schema? http://wiki.answers.com/Q/What_is_a_database_schema
<b>Check your understanding</b>:
* What does matplotlib pick as the x values if you don't supply them yourself?
* What tables are in the database?
* What options would you pass to <code>pyplot.plot</code> to generate a plot with red triangles and dotted lines?
* What is a schema?
* What fields are in the <code>category</code> table?
* What fields are in the <code>clue</code> table?
=== 2. Plotting the world population over time ===
=== 2. Query the database with SELECT ===
Run <code>python world_population.py</code>. This will pop up a window with a dot plot of the world population over the last 10,000 years.
Open <code>world_population.py</code>. Read through the code in this file.
In this example, we read our data from a file. Open the data file <code>world_population.txt</code> and examine the format of the file.
Try running the following queries from the sqlite prompt:
Find the documentation on http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.plot for customizing the linewidth of plots. Then change the world population plot to use a magenta, down-triangle marker and a linewidth of 2.
<b>World population resources</b>:
* <tt>SELECT * FROM category;</tt>
* <tt>SELECT NAME FROM category;</tt>
* <tt>SELECT * FROM clue;</tt>
* <tt>SELECT text, answer, value FROM clue;</tt>
* <tt>SELECT text, answer, value FROM clue LIMIT 10;</tt>
Explore the <code>category</code> and <code>clue</code> tables with your own SELECT queries.
<b>Check your understanding</b>:
* What does <code>*</code> mean in the above queries?
* What does the <code>LIMIT</code> SQL keyword do?
* Does case matter when making SQL queries?
<b>Step 2 resources</b>:
File input and output: http://docs.python.org/tutorial/inputoutput.html#reading-and-writing-files.
Using SELECT: http://www.w3schools.com/sql/sql_select.asp
Splitting sprints into parts based on a delimiter: http://www.hacksparrow.com/python-split-string-method-and-examples.html
<b>Check your understanding</b>:
* In <code>world_population.py</code>, what does <code>file("world_population.txt", "r").readlines()</code> return?
* In <code>world_population.py</code>, what does <code>point.split()</code> return?
=== 3. Make database queries from Python ===
=== 3. Plotting life expectancy over time ===
Examine the code in <code>jeopardy_categories.py</code>. To make a database query from Python, you need to:
# Import a Python library for making database connections
# Establish a connection to the desired database
# Get a cursor from the database for making queries
# Execute the database query using the standard SQL syntax
# Retrieve the list of results from the database cursor
# Do something useful with the results, like print them
# Close the database connection
In a new file, write code to plot the data in <code>life_expectancies_usa.txt</code>. The format in this file is <year>,<male life expectancy>,<female life expectancy>.
Match up each of these steps with lines of code in the file.
You can call <code>pyplot.plot</code> multiple times to draw multiple lines on the same figure. For example:
<pre>pyplot.plot(my_data_1, "mo-", label="my data 1")
=== 4. Tweak the existing Jeopardy scripts ===
pyplot.plot(my_data_2, "bo-", label="my data 2")</pre>
will plot <code>my_data_1</code> in magenta and <code>my_data_2</code> in blue on the same figure.
==== 1. Modify <code>jeopardy_categories.py</code> to print both the category and game number ====
Supply labels for your plots, like above. Then use <code>pyplot.legend</code> to give your graph a legend. Just plain <code>pyplot.legend()</code> will work, but providing more options may give a better effect.
<b>tip</b>: Remind yourself of the <code>categories</code> schema by running <code>.schema category</code> at a sqlite prompt.
<br />
Your graph should look something like this:
<br>Example output</b>:
<pre>Example categories:
SEAN SONG (game #2)
NEW YORK CITY (game #6)
LITTLE RED RIDING HOOD (game #8)</pre>
To save your graph to a file instead of or in addition to displaying it, call <code>pyplot.savefig</code>.
==== 2. Modify <code>jeopardy_clues.py</code> to only print clues with an $800 value. ====
<b>Life expectancy resources</b>:
A good way to achieve this is by adding a <code>WHERE</code> clause to the SQL query in <code>jeopardy_clues.py</code>.
Read about <code>WHERE</code> clauses in this short document:
* The WHERE Clause: http://www.w3schools.com/sql/sql_where.asp
<br />
<b>Example output</b>:
<pre>Example clues:
A: She also created the detectives Tuppence &amp; Tommy Beresford
Q: What is 'Agatha Christie'
A: According to this Old Testament book, this &quot;swords into plowshares&quot; prophet walked naked for 3 years
Q: What is 'Isaiah'
=== 5. Daily Doubles ===
Write a script that prints 10 daily doubles and their responses.
<br />
<b>tip</b>: The <code>clue</code> table has an <code>isDD</code> field.
<br />
<b>Example output</b>:
<pre>Category: NEW YORK CITY
Question: The heart of Little Italy is this street also found in a Dr. Seuss book title
Answer: Mulberry Street
Question: This Mideastern boundary river rises on the slopes of Mount Hermon
Answer: the Jordan
Category: ROOM
Question: The Titanic has 3 rooms for this--only men were allowed there, as women weren't supposed to do it in public
Answer: smoking
==Bonus exercises==
=== 1. Random category clues ===
Write a script that randomly chooses a category and prints clues from that category.
<br />
<b>tip</b>: SQL supports an "<code>ORDER BY RANDOM()</code>" clause that will return rows in a random order. For example, to randomly pick 1 category id you could use:
<pre>SELECT id FROM category ORDER BY RANDOM() LIMIT 1</pre>
You can also use <code>ORDER BY</code> to sort the clues by value.
<br />
<b>Example output</b>:
[$200] Last name of Moe of the Three Stooges
[$400] Moe Strauss founded this auto parts chain along with Manny Rosenfield &amp; Jack Jackson
[$600] Major league catcher Moe Berg was also a WWII spy for this agency, precursor of the CIA
[$800] Term for the type of country music Moe Bandy plays, the clubs where he began, or the &quot;Queen&quot; he sang of in 1981
[$1000] This &quot;Kool&quot; rapper's album &quot;How Ya Like Me Now&quot; began a rivalry with LL Cool J</pre>
<b>Exercises resources</b>:
File input and output: http://docs.python.org/tutorial/inputoutput.html#reading-and-writing-files.
Using ORDER BY: http://www.w3schools.com/sql/sql_orderby.asp
Splitting sprints into parts based on a delimiter: http://www.hacksparrow.com/python-split-string-method-and-examples.html
Examples of legends: http://matplotlib.sourceforge.net/examples/pylab_examples/legend_auto.html
Ways to configure your legend: http://matplotlib.sourceforge.net/api/legend_api.html
Saving your graph to a file: http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.savefig
==Bonus exercises==
=== 1. Letter frequency analysis of the US Constitution ===
=== 2. Random game categories ===
Write a script to randomly choose a game number and print the categories from that game.
<br />
<b>tip</b>: the <code>category</code> table has <code>game</code> and <code>round</code> fields. round 0 is the Jeopardy round, round 1 is the Double Jeopardy round, and round 2 is Final Jeopardy.
<br />
<b>Example output</b>:
<pre>Categories for game #136:
0 FILE UNDER &quot;M&quot;
2 IN THE NEWS 2000</pre>
# Run <code>python constitution.py</code>. It will generate a bar chart showing the frequency of each letter in the alphabet in the US Constitution.
# Open and read through <code>constitution.py</code>. The code for gathering and displaying the frequencies is a bit more complicated than the previous scripts in this projects, but try to trace the general strategy for plotting the data. Be sure to read the comments!
# Try to answer the following questions:
## On line 11, what is <code>string.ascii_lowercase</code>?
## On line 18, what is the purpose of <code>char = char.lower()</code>?
## What are the contents of <code>labels</code> after the <code>for</code> loop on line 30 completes?
## On line 41, what are the two arguments passed to <code>pyplot.xticks</code>
## On line 44, we use <code>pyplot.bar</code> instead of our usual <code>pyplot.plot</code>. What are the 3 arguments passed to <code>pyplot.bar</code>?
# We've included a mystery text file <code>mystery.txt</code>: an excerpt from an actual novel. Alter <code>constitution.py</code> to process the data in <code>mystery.txt</code> instead of <code>constitution.txt</code>, and re-run the script. What do you notice that is odd about this file? You can read more about this odd novel [http://en.wikipedia.org/wiki/Gadsby_(novel) here].
=== 3. Top 20 Jeopardy categories ===
=== 2. Tour the matplotlib gallery ===
Read about the <code>GROUP BY</code> clause and write a script using it to print the 20 most common Jeopardy categories.
You can truly make any kind of graph with matplotlib. You can even create animated graphs. Check out some of the amazing possibilities, including their source code, at the matplotlib gallery: http://matplotlib.sourceforge.net/gallery.html.
An example of using <code>GROUP BY</code> and <code>ORDER BY</code> to produce an ordered list of counts on a hypothetical <code>foo</code> field is:
<pre>SELECT foo, COUNT(foo) AS count FROM my_table GROUP BY foo ORDER BY count</pre>
<b>Example output</b>:
You've learnedread, about SQLmodified, and makingcreated databasescripts that plot and queriesanalyze fromdata withinusing Pythonmatplotlib. Keep practicing!
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