Category: machine learning

Predicting Employee Turnover at SIOP 2018

The 2018 annual Society for Industrial and Organizational Psychology (SIOP) conference featured its first-ever machine learning competition. Teams competed for several months in predicting the enployee turnover (or churn) in a large US company. A more complete introduction as presented at the conference can be found here. All submissions had to be open source and the winning submissions have been posted in this GitHub repository. The winning teams consist of analysts working at WalMart, DDI, and HumRRO. They mostly built ensemble models, in Python and/or R, combining algorithms such as (light) gradient boosted trees, neural networks, and random forest analysis.

Open Source Visual Inspector for Neuroevolution (VINE)

Open Source Visual Inspector for Neuroevolution (VINE)

In optimizing their transportation services, Uber uses evolutionary strategies and genetic algorithms to train deep neural networks through reinforcement learning. A lot of difficult words in one sentence; you can imagine the complexity of the process.

Because it is particularly difficult to observe the underlying dynamics of this learning process in neural network optimization, Uber built VINE – a Visual Inspector for NeuroEvolution. VINE helps to discover how evolutionary strategies and genetic optimizing are performing under the hood. In a recent article, they demonstrate how VINE works on the Mujoco Humanoid Locomotion task.

[…] In the Humanoid Locomotion Task, each pseudo-offspring neural network controls the movement of a robot, and earns a score, called its fitness, based on how well it walks. [Evolutionary principles] construct the next parent by aggregating the parameters of pseudo-offspring based on these fitness scores […]. The cycle then repeats.

Uber, March 2018, link

VINE plots parent neural networks and their pseudo-offspring according to their performance. Users can then interact with these plots to:

  • visualize parents, top performance, and/or the entire pseudo-offspring cloud of any generation,
  • compare between and within generation performance,
  • and zoom in on any pseudo-offspring (points) in the plot to display performance information.

The GIFs below demonstrate what VINE is capable of displaying:

The evolution of performance over generations. The color changes in each generation. Within a generation, the color intensity of each pseudo-offspring is based on the percentile of its fitness score in that generation (aggregated into five bins). [original]
Vine allows user to deep dive into each single generation, comparing generations and each pseudo-offspring within them [original]
VINE can be found at this link. It is lightweight, portable, and implemented in Python.

Identifying “Dirty” Twitter Bots with R and Python

Past week, I came across two programming initiatives to uncover Twitter bots and one attempt to identify fake Instagram accounts.

Mike Kearney developed the R package botornot which applies machine learning to estimate the probability that a Twitter user is a bot. His default model is a gradient boosted model trained using both users-level (bio, location, number of followers and friends, etc.) and tweets-level information (number of hashtags, mentions, capital letters, etc.). This model is 93.53% accurate when classifying bots and 95.32% accurate when classifying non-bots. His faster model uses only the user-level data and is 91.78% accurate when classifying bots and 92.61% accurate when classifying non-bots. Unfortunately, the models did not classify my account correctly (see below), but you should definitely test yourself and your friends via this Shiny application.

Fun fact: botornot can be integrated with Mike’s rtweet package

Scraping Dirty Bots

At around the same time, I read this very interesting blog by Andy Patel. Annoyed by the fake Twitter accounts that kept liking and sharing his tweets, Andy wrote a Python script called pronbot_search. It’s an iterative search algorithm which Andy seeded with the dozen fake Twitter accounts that he identified originally. Subsequently, the program iterated over the friends and followers of each of these fake users, looking for other accounts displaying similar traits (e.g., similar description, including an URL to a sex-website called “Dirty Tinder”).

Whenever a new account was discovered, it was added to the query list, and the process continued. Because of the Twitter API restrictions, the whole crawling process took literal days before Andy manually terminated it. The results are just amazing:

After a day, the results looked like so. Notice the weird clusters of relationships in this network. [original]
The full bot network uncovered by Andy included 22.000 fake Twitter accounts:

At the end of the weekend of March 10th, Andy had to stop the scraper after running for several days even though he had only processed 18% of the networks of the 22.000 included Twitter bots [original]
The bot network on Twitter is probably enormous! Zooming in on the network, Andy notes that:

Pretty much the same pattern I’d seen after one day of crawling still existed after one week. Just a few of the clusters weren’t “flower” shaped.

Andy Patel, March 2018, link

Zoomed in to a specific part of the network you can see the separate clusters of bots doing little more than liking each others messages. [original]
In his blog, Andy continues to look at all kind of data on these fake accounts. I found most striking that many of these account are years and years old already. Potentially, Twitter can use Mike Kearney’s botornot application to spot and remove them!

Most of the bots in the Dirty Tinder network found by Andy Patel were 3 to 8 years old already. [original]
Andy was nice enough to share the data on these bot accounts here, for you to play with. His Python code is stored in the same github repo and more details around this project you can read in his original blog.

Fake Instagram Accounts

Finally, SRFdata (Timo Grossenbacher) attempted to uncover fake Instagram followers among the 7 million followers in the network of 115 important Swiss Instagram influencers in R. Magi Metrics was used to retrieve information for public Instagram accounts and rvest for private accounts. Next, clear fake accounts (e.g., little followers, following many, no posts, no profile picture, numbers in name) were labelled manually, and approximately 10% of the inspected 1000 accounts appeared fake. Finally, they trained a random forest model to classify fake accounts with a sensitivity (true negative) rate of 77.4% and an overall accuracy of around 94%.

Predictive HR Analytics

Predictive HR Analytics

Tilburg University has set up a masterclass Predictive HR Analytics. In 3 days, the Professional Learning program will teach you all you need to know to implement predictive analytics and take HR to the next level. More information can be found here.

What makes this program unique?

  • The masterclass Predictive HR Analytics goes beyond HR analytics and focuses on transformational people predictions. You learn how to embed predictive HR analytics into your HR Strategy and how to use your findings to convince others.
  • The masterclass is developed at the prestigious Human Resources department at Tilburg University, which has obtained international recognition with its high-quality academic research in the HRM field.
  • The mix of professors in conjunction with leading HR professionals leads to a strong academic program with a practical approach.
  • Your peer participants will make sure that the class opens up a high-quality network of HR specialists. The diversity of leading companies from different sectors in the classroom creates new insights for all the participants.
  • The program is like a 3-day pressure cooker. By combining online and offline components, we can create more in-depth discussions in the classroom.
  • You will experience a high impact on your daily practice, since the program is focused on direct implementation.

Your profile

This course is ideal for anyone in HR seeking to become more adept in using quantitative data for decision making. Typical participants are (future) HR analysts, HR managers, HR business partners, HR consultants and (financial) business analysts with a strong link on people resources. Participants are from various sectors, such as financial services, healthcare institutions, government agencies and business services.

Super Resolution: A Photo Enhancer AI

In the video below, one of my favorite YouTube channels (Two Minute Papers) discusses a new super resolution project where academic scholars taught a neural network to improve low quality photo’s. The researchers took the same picture with multiple camera’s of varying quality and allowed a neural network to learn how the lowest quality pictures can be adjusted to more closely resemble their high quality counterparts. A very interesting approach and the results are just mind-boggling:

photo_super_resolution.png

The scholars were nice enough to not only publish the paper open access, but also to open source the data. You can download a 125 Mb sample here or the original full 64 GB dataset here.

Machine Learning and AI courses at Google

Machine Learning and AI courses at Google

Google has announced to provide open access to its artificial intelligence and machine learning courses. On their overview page, you will find many educational resources from machine learning experts at Google. They announced to share AI and machine learning lessons, tutorials and hands-on exercises for people at all experience levels. Simply filter through the resources and start learning, building and problem-solving.

For instance, up your game straight away with this 15-hour Machine Learning crash course. Zuri Kemp – who leads Google’s machine learning education program – said that over 18,000 Googlers have already enrolled in the course. Designed by the engineering education team, the courses explores loss functions and gradient descent and teached you to build your own neural network in Tensorflow.