Project 2: Twitter Trends

What do people tweet?
Draw their feelings on a map
to discover trends.


In this project, you will develop a geographic visualization of twitter data across the USA. You will need to use dictionaries, lists, and data abstraction techniques to create a modular program. This project uses ideas from Sections 2.1-2.4 of the lecture notes.

The map displayed above depicts how the people in different states feel about Texas. This image is generated by:

  1. Collecting public Twitter posts (tweets) that have been tagged with geographic locations and filtering for those that contain the "texas" query term,
  2. Assigning a sentiment (positive or negative) to each tweet, based on all of the words it contains,
  3. Aggregating tweets by the state with the closest geographic center, and finally
  4. Coloring each state according to the aggregate sentiment of its tweets. Red means positive sentiment; blue means negative.

The details of how to conduct each of these steps is contained within the project description. By the end of this project, you will be able to map the sentiment of any word or phrase. There are two alternative zip archives related to this project:

The project uses several files, but all of your changes will be made to the first one.

A starter implementation of the main project file.

Geographic positions, 2-D projection equations, and geographic distance functions.

Functions for drawing maps.

Functions for loading Twitter data from files.

A simple Python graphics library.

Utility functions for 61A.

The data directory contains all the data files needed for the project. The above zip archives contain this directory, but if you download the individual project files above, you will need to download the data directory as well.


This is a one-week project. You'll work in a team of two people, and you can complete all problems together with your partner.

Start early! Feel free to ask for help early and often. The course staff is here to assist you, but we can't help everyone an hour before the deadline. Piazza awaits. You are not alone!

In the end, you and your partner will submit one project. There are 19 possible points (16 for correctness and 3 for composition). You only need to submit the file You do not need to modify any other files for this project. To submit the project, change to the directory where the file is located and run submit proj2.

Phase 1: The Feelings in Tweets

In this phase, you will create an abstract data type for tweets, split the text of a tweet into words, and calculate the amount of positive or negative feeling in a tweet.


First, you will implement an abstract data type for Tweets. The constructor make_tweet is defined at the top of make_tweet returns a python dictionary with the following entries:

  text:      a string, the text of the tweet, all in lowercase
  time:      a datetime object, when the tweet was posted
  latitude:  a floating-point number, the latitude of the tweet's location
  longitude: a floating-point number, the longitude of the tweet's location

Problem 1 (1 pt). Implement the tweet_words and tweet_time selectors. Call extract_words to list the words in the text of a tweet.

Problem 2 (1 pt). Implement the tweet_location selector, which returns a position. Positions are another abstract data type, defined at the top of Make sure that you understand how to manipulate positions; they play an important role in this project.

When you complete problems 1 and 2, the doctest for make_tweet should pass.

python3 -t make_tweet

Problem 3 (1 pt). Improve the extract_words function as follows: Assume that a word is any consecutive substring of text that consists only of ASCII letters. The string ascii_letters in the string module contains all letters in the ASCII character set. The extract_words function should list all such words in order and nothing else.

When you complete this problem, the doctest for extract_words should pass.

python3 -t extract_words

Problem 4 (1 pt). Implement the sentiment abstract data type, which represents a sentiment value that may or may not exist. The constructor make_sentiment takes either a numeric value within the interval -1 to 1, or None to indicate that the value does not exist. Implement the selectors has_sentiment and sentiment_value as well. You may use any representation you choose, but the rest of your program should not depend on this representation.

When you complete this problem, the doctests for make_sentiment and get_word_sentiment should pass. You can also call the print_sentiment function to print the sentiment values of all sentiment-carrying words in a line of text.

python3 -t make_sentiment
python3 -t get_word_sentiment
python3 -p computer science is my favorite!
python3 -p life without lambda: awful or awesome?

Problem 5 (1 pt). Implement analyze_tweet_sentiment, which takes a tweet (of the abstract data type) and returns a sentiment. Read the docstrings for get_word_sentiment and analyze_tweet_sentiment to understand how the two functions interact. Your implementation should not depend on the representation of a sentiment!.

When you complete this problem, the doctests for analyze_tweet_sentiment should pass.

python3 -t analyze_tweet_sentiment

Phase 2: The Geometry of Maps


We will use the position abstract data type to represent geographic latitude-longitude positions on the Earth. The data abstraction, defined at the top of, has the constructor make_position and the selectors latitude and longitude.

In this phase, you will write two functions that together determine the centers of U.S. states. The shape of a state is represented as a list of polygons. Some states (e.g. Hawaii) consist of multiple polygons, but most states (e.g. Colorado) consist of only one polygon (still represented as a length-one list).

Problem 6 (2 pt). Implement find_centroid, which takes a polygon and returns three values: the coordinates of its centroid and its area. The input polygon is represented as a list of position abstract data types, which are the consecutive vertices of its perimeter. The first vertex is always identical to the last.

The centroid of a two-dimensional shape is its center of balance, defined as the intersection of all straight lines that evenly divide the shape into equal-area halves. find_centroid returns the centroid and area of an individual polygon.

The formula for computing the centroid of a polygon appears on Wikipedia. The formula relies on vertices being consecutive (either clockwise or counterclockwise; both give the same answer), a property that you may assume always holds for the input.

The area of a polygon is never negative. Depending on how you compute the area, you may need to use the built-in abs function to return a non-negative number.

When you complete this problem, the doctest for find_centroid should pass.

python3 -t find_centroid

Problem 7 (2 pt). Implement find_center, which takes a shape represented by a list of polygons and returns a position, its centroid.

The centroid of a collection of polygons can be computed by geometric decomposition. The centroid of a shape is the weighted average of the centroids of its component polygons, weighted by their area.

When you complete this problem, the doctest for find_center should pass.

python3 -t find_center

Once you are finished, draw_centered_map will draw the 10 states closest to a given state (including that state).

python3 -d CA

Phase 3: The Mood of the Nation


The name us_states is bound to a dictionary containing the shape of each U.S. state, keyed by its two-letter postal code. You can use the keys of this dictionary to iterate over all the U.S. states.

In this phase, you will write functions to determine the state that a tweet is coming from, group tweets by state, and calculate the average positive or negative feeling in all the tweets associated with a state.

Problem 8 (1 pt). Implement find_closest_state, which returns the two-letter postal code of the state that is closest to the location of a tweet. Use the geo_distance function (provided in to calculate the shortest distance in miles between two positions.

When you complete this problem, the doctests for find_closest_state should pass.

python3 -t find_closest_state

Problem 9 (1 pt). Implement group_tweets_by_state, which takes a sequence of tweets and returns a dictionary. The keys of the returned dictionary are state names (two-letter postal codes), and the values are lists of tweets that appear closer to that state's center than any other.

When you complete this problem, the doctests for group_tweets_by_state should pass.

python3 -t group_tweets_by_state

Problem 10 (1 pt). As an exercise, implement most_talkative_state, which returns the state containing the most tweets containing a given term.

When you complete this problem, the doctests for most_talkative_state should pass.

python3 -t most_talkative_state

Problem 11 (2 pt). Implement average_sentiments. This function takes the dictionary returned by group_tweets_by_state and also returns a dictionary. The keys of the returned dictionary are the state names (two-letter postal codes), and the values are average sentiment values for all the tweets in that state.

If a state has no tweets with sentiment values, leave it out of the returned dictionary entirely. Do not include a state with no sentiment using a zero sentiment value. Zero represents neutral sentiment, not unknown sentiment. States with unknown sentiment will appear gray, while states with neutral sentiment will appear white.

You should now be able to draw maps that are colored by sentiment corresponding to tweets that contain a given term.

python3 -m sandwich
python3 -m obama
python3 -m texas
python3 -m my life
If you downloaded the small version of the project, you will only be able to map these four terms. If you would like to map any term, you will need to download this Twitter data file and place it in the data directory of your project.

Phase 4: Into the Fourth Dimension

In this last section, you will take into account the fourth dimension: time. Each tweet has a datetime object, which represents the time that the tweet was posted.

The provided draw_map_by_hour function visualizes the tweets that were posted during each hour of the day. For example, "sandwich" tweets appear most positive at 10:00pm: late night snack!

Problem 12 (2 pt). Implement group_tweets_by_hour. which takes a sequence of tweets and returns a dictionary. The keys of the returned dictionary are the integers 0 through 23, representing the 24 hours of the day. The value for each key is a list of the tweets that were posted during that hour.

To get started, read the online documentation on datetime objects. When you are finished, you can visualize the changing sandwich sentiments over time.

python3 -b sandwich

Congratulations! One more 61A project completed.


These extensions are optional and ungraded. In this class, you are welcome to program just for fun. If you build something interesting, come to office hours and give us a demo. However, please do not change the behavior or signature of the functions you have already implemented.

Acknowledgements: Aditi Muralidharan developed this project with John DeNero. Hamilton Nguyen extended it.

Extra info about this assignment: