Free courses at Kaggle

I recently found out that Kaggle has a set of free courses for learning AI skills.

Screenshot from Kaggle.com

The first course is an introduction to Python, and these are the course modules:

  1. Hello, Python: A quick introduction to Python syntax, variable assignment, and numbers
  2. Functions and Getting Help: Calling functions and defining our own, and using Python’s builtin documentation
  3. Booleans and Conditionals: Using booleans for branching logic
  4. Lists: Lists and the things you can do with them. Includes indexing, slicing and mutating
  5. Loops and List Comprehensions: For and while loops, and a much-loved Python feature: list comprehensions
  6. Strings and Dictionaries: Working with strings and dictionaries, two fundamental Python data types
  7. Working with External Libraries: Imports, operator overloading, and survival tips for venturing into the world of external libraries

Even though I’m an intermediate Python coder, I skimmed all the materials and completed the seven problem sets to see how they are teaching Python. The problems were challenging but reasonable, but the module on functions is not going to suffice for anyone who has little prior experience with programming languages. I see this in a lot of so-called introductory materials — functions are glossed over with some ready-made examples, and then learners have no clue how returns work, or arguments, etc.

At the end of the course, the learner is encouraged to join a Kaggle competition using the Titanic passengers dataset. However, the learner is hardly prepared to analyze the Titanic data at this point, so really this is just an introduction to how to use files provided in a competition, name your notebook, save your work, and submit multiple attempts. The tutorial gives you all the code to run a basic model with the data, so it’s really more a demo than a tutorial.

My main interest is in the machine learning course, which I’ll begin looking at today.

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AI in Media and Society by Mindy McAdams is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
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What is a neural network and how does it work?

The most wonderful thing about YouTube is you can use it to learn just about anything.

One of the 10,000 annoying things about YouTube is finding a good, satisfying version of the lesson you want to learn can take hours of searching. This is especially true of videos about technical aspects of machine learning. Of course there are one- and two-hour recordings of course lectures by computer science professors. But I’ve been seeking out shorter videos with more animations and illustrations of concepts.

Understanding what a neural network is and how it processes data is necessary to demystifying machine learning. Data goes in, results come out — but in between is a “black box” consisting of code and hardware. It sort of works like a human brain, and yet, it really doesn’t.

So here at last is a painless, math-free video that walks us through a neural network. The particular example shown uses the MNIST dataset, which consists of 70,000 images of handwritten digits, 0–9. So the task being performed is the recognition of those digits. (This kind of system can be used to sort mail using postal codes, for example.)

What you’ll see is how the first layer (a vertical line of circles on the left side) represents the input. If each of the MNIST images is 28 pixels wide by 28 pixels high, then that first layer has to represent 784 pixels and each of their color values — which is a number. (One image is the input — only one at a time.)

The final vertical layer, all the way to right side, is the output of the neural network. In this example, the output tells us which digit was in the input — 0, 1, 2, etc. To see the value in this, go back to the mail-sorting idea. If a system can read postal codes, it recognizes several numbers and then transmits them to another system that “knows” which postal code goes to which geographical location. My letter gets sorted into the Florida bin and yours into the bin for your home.

In between the input and the output are the vertical “hidden” layers, and that’s where the real work gets done. In the video you’ll see that the number of circles — often called neurons, but they can also be called just units — in a hidden layer might well be less than the number of units in the input layer. The number of units in the output layer can also differ from the numbers in other layers.

When the video describes edge detection, you might recall an earlier post here.

Beautifully, during an animation, our teacher Grant Sanderson explains and shows that the weights exist not in or on the units (the “neurons”) but in fact in or on the connections between the units.

Okay, I lied a little. There is some math shown here. The weight assigned to the connection is multiplied by the value of the unit to the left. The results are all summed, for all left-side units, and that sum is assigned to the unit to the right (meaning the right side of that one connection).

The video bogs down just a bit between the Sigmoid squishification function and applying the bias, but all you really need to grasp is that the value of the right-side unit shows whether or not that little region of the image (in this case, it’s an image) has a significant difference. The math is there to determine if the color, the amount of color, is significant enough to count. And how much it should count.

I know — math, right?

But seriously, watch the video. It’s excellent.

“And that’s a lot to think about! With this hidden layer of 16 neurons, that’s a total of 784 times 16 weights, along with 16 biases. And all of that is just the connections from the first layer to the second.”

—Grant Sanderson, But what is a neural network? (video)

Sanderson doesn’t burden us with the details of the additional layers. Once you’ve seen the animations for that first step — from the input layer through the connections to the first hidden layer — you’ll have a real appreciation for what’s happening under the hood in a neural network.

In the final 6 minutes of this 19-minute video, you’ll also learn how the “learning” takes place in machine learning when a neural net is involved. All those weights and bias values? They are not determined by humans.

“Digging into what the weights and biases are doing is a good way to challenge your assumptions and really expose the full space of possible solutions.”

—Grant Sanderson, But what is a neural network? (video)

I confess it does get rather mathy at the end, but hang on through the parts that are beyond your personal math background and listen to what Sanderson is telling us. You can get a lot out of it even if the equation itself is like hieroglyphics to you.

The video content ends at 16:26, followed by the usual “subscribe to my channel” message. More info about Sanderson and his excellent videos is on his website, 3Blue1Brown.

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AI in Media and Society by Mindy McAdams is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
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Getting thrown into machine learning

Early in 2018, I had several senior journalism students who wanted to learn about machine learning. I knew nothing about it, and they knew that, and we plowed forward together.

The three student teams chose these topics:

  • Sentiment analysis on subreddits for NBA teams
  • Analysis of county court documents naming our university
  • Analysis of tweets by one news organization for audience reactions, engagements

We quickly learned that knowing Python was a big plus. (Fortunately, we all knew Python.) Each of the teams found a different Python library to work with, and after a few weeks, projects were completed and demonstrated — although desired results were not achieved in all cases.

I crammed information mainly from two sources — a YouTube video series called Machine Learning Recipes with Josh Gordon, and something I’ve lost that explained in detail how a model was trained on the Iris Data Set. These provided a surprisingly solid foundation for beginning to understand how today’s machine learning projects are done.

Above: Histograms and features from the Iris Data Set

Since then, I’ve continued to read casually about AI and machine learning. As more and more articles have appeared in the general press and news reports about face recognition and self-driving cars (among other topics related to AI), it’s become clear to me that journalism students need to know more about these technologies — if for no other reason than to avoid being bamboozled by buzzword-spewing politicians or tech-company flacks.

Since May 2020, I’ve been collecting resources, reading and researching, with an intention to teach a course about AI for communications students in spring 2021. This new blog is going to help me organize and prioritize articles, posts, videos, and more.

If it helps other people get a handle on AI, so much the better!

Creative Commons License
AI in Media and Society by Mindy McAdams is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Include the author’s name (Mindy McAdams) and a link to the original post in any reuse of this content.