Visualizing Fitbit GPS Data

Sat May 01 2021

This post looks at how you can aggregate and visualize Fitbit GPS data since there is no built-in functionality to do this on the Fitbit website. Before you read this post, check out my two other posts on using Fitbit data:

• A Closer Look at Fitbit Data
• Graphing my Life with Matplotlib

1 Getting the Data

There are two options that we can use to fetch data from Fitbit:

• Fitbit’s Data Export Tool
• Fitbit’s API

1.1 Exporting from the Website

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Quadtree Animations with Matplotlib

Mon Feb 08 2021

This post will extend my last post on image quadtrees to create an animation that varies the quadtree splitting threshold. Like all recursively dividing algorithms, as you relax the splitting parameter, more partitions get generated. Although this principle makes intuitive sense, seeing animation tells a fuller story.

This post will be using the matplotlib’s animation functionality and the quadtree code I wrote in my previous post. The following code snippet illustrates a simple animation using matplolib:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib.animation import FuncAnimation

fig = plt.figure()
ax = plt.axes(xlim=(0, 4), ylim=(-2, 2))
line, = ax.plot([], [], lw=3)

def init():
    line.set_data([], [])
    return line,
def animate(i):
    x = np.linspace(0, 4, 1000)
    y = np.sin(2 * np.pi * (x - 0.01 * i))
    line.set_data(x, y)
    return line,

anim = FuncAnimation(fig, animate, init_func=init,
                               frames=200, interval=20, blit=True)

anim.save('Wave.gif')

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Implementing a Quadtree in Python

Sat Oct 10 2020

This blog post is the first part of a multi-post series on using quadtrees in Python. This post goes over quadtrees’ basics and how you can implement a basic point quadtree in Python. Future posts aim to apply quadtrees in image segmentation and analysis.

A quadtree is a data structure where each node has exactly four children. This property makes it particularly suitable for spatial searching. Quadtrees are generalized as “k-d/k-dimensional” trees when you have more than 4 divisions at each node. In a point-quadtree, leaf nodes are a single unit of spatial information. A quadtree is constructed by continuously dividing each node until each leaf node only has a single node inside of it. However, this partitioning can be modified so that each leaf node contains no more than K elements or that each cell can be at a maximum X large. This stopping criterion is similar to that of the stopping criteria when creating a decision tree.

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Node2vec With Steam Data

Sun Jul 26 2020

Graph algorithms!!! Working with graphs can be a great deal of fun, but sometimes we just want some cold hard vectors to do some good old-fashioned machine learning. This post looks at the famous node2vec algorithm used to quantize graph data. The example I’m giving in this blog post uses data from my recently resurrected steam graph project.

If you live under a rock, Steam is a platform where users can purchase, manage, and play games with friends. Although there is a ton of data within the Steam network, I am only interested in the graphs formed connecting users, friends, and games. My updated visualization to show a friendship network looks like this:

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Time Spent In Steam Games

Mon Jul 20 2020

Last week I scrapped a bunch of data from the Steam API using my Steam Graph Project. This project captures steam users, their friends, and the games that they own. Using the Janus-Graph traversal object, I use the Gremlin graph query language to pull this data. Since I am storing the hours played in a game as a property on the relationship between a player and a game node, I had to make a “join” statement to get the hours property with the game information in a single query.

Object o = graph.con.getTraversal()
    .V()
    .hasLabel(Game.KEY_DB)
    .match(
            __.as("c").values(Game.KEY_STEAM_GAME_ID).as("gameID"),
            __.as("c").values(Game.KEY_GAME_NAME).as("gameName"),
            __.as("c").inE(Game.KEY_RELATIONSHIP).values(Game.KEY_PLAY_TIME).as("time")
    ).select("gameID", "time", "gameName").toList();
WrappedFileWriter.writeToFile(new Gson().toJson(o).toLowerCase(), "games.json");

Using the game indexing property on the players, I noted that I only ended up wholly indexing the games of 481 players after 8 hours.

graph.con.getTraversal()
    .V()
    .hasLabel(SteamGraph.KEY_PLAYER)
    .has(SteamGraph.KEY_CRAWLED_GAME_STATUS, 1)
    .count().next()

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