Unfortunately, datasets aren't as easy to gauge as the butterflies in this picture. Yet, even if the simpler cases where we can make a descriptive plot to highlight the geometry involved, similarity is not a binary matter. Two datasets may be somewhat similar or dissimilar, without being identical or in stark contrast. So, how could we gauge similarity in an N-dimensional space?

The simplest thing to do is run a bunch of t-tests, one for each variable involved. This approach may be fine for someone new to the field (especially if the people managing this person's team aren't knowledgeable about these matters), but it won't work well. There are several underlying assumptions in this strategy that rob it of its validity and, possibly, its effectiveness.

The Index of Congruence is a simple heuristic based on the Index of Peculiarity, which in turn is congruent to the Index of Discernibility (though not focused on classification scenarios per se). The Index of Congruence does one simple thing: gauge the similarity of two matrices of real numbers on a scale of 0 to 1 with high values denoting strong similarity. It's not perfect but it does what it sets out to do, and does so swiftly. If one of the datasets is larger than a given threshold, some (random) sampling takes place in both datasets, preserving the original ratio in sizes, before the heuristic is applied. Also, normalization takes place in the back-end without worrying the user, since we have better things to do than worry about the scale of the variables at hand, right?

I could write about this heuristic for a while, but I'm sure you'd rather see it in action. So, I'm attaching a Jupyter notebook that you can check out on your own. No, I haven't switched to this kind of code notebook as I'm still in favor of Neptune notebooks, but when it comes to showcasing something, Jupyter notebooks remain the best option. Cheers!
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Lately I published an episode of my podcast where I talk about compression and encryption as privacy tools (link). That’s all nice and dandy but how do we do any of that in practice? Well, most compression programs have an encryption option, which may be sufficient for low-confidentiality documents. But what about datasets that contain lots of PII? And if you are like me, you may use Julia for processing them, since it’s by far the most efficient programming language for the task, that’s also high-level.

​Enter ComCrypt, a simple script that does high-quality compression and quantum-proof encryption all in one go. Namely, it makes use of the CDF script which I’ve talked about before (it’s been about two years since I created it) for compressing the data into an archive having the .cdf extension (which stands for compressed data format and it’s native to Julia). Then it applies ThunderStorm to it, using an external key file. If anything goes wrong throughout this process, ComCrypt alerts the user with some error message informing about the part that threw the error. Otherwise, it yields a message saying that the data has been compressed successfully. The reverse process shares the same philosophy. 

​Currently, ComCrypt at its first version so its scope is a bit limited (e.g., it handles only a single data object per file). However, there are ways to make it more usable and useful. In any case, it’s already a useful little tool for keeping your data safe when working in the Julia environment. Also, it’s very light on the dependencies (just one external library and a few Julia scripts). Cheers.

Overview
I've been working on this cipher for several years now, and although it's not the first one I've developed, it's the best one, so far. Not just in terms of security but also in speed and customization. I haven't touched the algorithm in a couple of years now, but I recently did some updates on its shell functions and its GUI for better usability. But I'm getting ahead of myself. Let's start with some basics first, in case you are not familiar with it.

What ThunderStorm Is
ThunderStorm is a semi-symmetric encryption system designed for codes impenetrable by  conventional cryptanalysis methods. Unlike other encryption methods, it doesn't rely on prime  numbers and factoring, while it employs true randomness in the keys it uses for additional security. It currently exists in two versions: one that's order-sensitive and one that's purely symmetric and  order-indifferent. The former makes for a stronger cipher, while the latter is lighter.  ThunderStorm is implemented entirely in Julia (recently tested in v.1.7.2 with no issues) and has minimal dependencies on any libraries.

How It Works
In a nutshell, ThunderStorm works as follows. It captures all the relevant information regarding the  size of the original file and its hash. It then encrypts it using the hash of the key. This is the header  of the encrypted archive. Then a random amount of noise is created and added to the original file.  After that, the data is encrypted and shuffled using the key, in a byte-wise fashion. The resulting  archive, which is somewhat larger than the original is outputted using a file extension that makes it  clear what it is. For the decryption process, the reverse is done. Note that if a single bit in the key  file is off, the decryption process won't work, or if it does, it will yield a completely different file  that would be unrecognizable. Also, if you were to take a random byte in the encrypted archive  there is no way of knowing if that byte is an encrypted part of the original file (it could be just  noise) or if it is which part of the file it comes from or what it is exactly. Also, only part of the key  is usually used for the encryption, while its parts are shuffled before being utilized in the encryption  process. I had published a video on ThunderStorm back in my Safari days, but it's no longer available since the contract with O'Reilly (which acquired Safari at one point) came to an end.

ThunderStorm Use Cases
The ThunderStorm system has several real-world use cases. Primarily, it is ideal for individual use,  particularly for static documents (e.g., a password archive, financial records, etc.). This includes  documents that are stored in the cloud or a web server. Additionally, ThunderStorm can be modified  to be used for exchanging sensitive documents, where increased cybersecurity is a requirement. For  all the use cases, large encryption keys are strongly recommended, something possible through an  auxiliary method of the ThunderStorm system. A large key can be manufactured in such a way that  it has zero ectropy (i.e., maximal entropy possible), making cryptanalysis extremely difficult if not  altogether impossible. The fact that keys can be reused in ThunderStorm with minimal risk is an  asset that can be harnessed for efficiency.

Latest Improvements
Since I'm a big fan of continuous improvement (Total Quality Management), I decided to make a GUI for ThunderStorm, even though I'm not a GUI kind of guy. Still, after having developed my BASH scripting skills enough, I was able to do that. So, recently I came up with a new script that leverages a few window screens to facilitate the use of this program. It still uses Julia on the back-end, but it can run directly from the shell (or the file manager, if you prefer). Below are some screenshots of the interactive aspects of that script. Note that some of the functionality of ThunderStorm was removed to make the whole program easier for the average user. For the more tech-savvy users, the functionality remains and can be accessed through the corresponding Julia scripts.
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Parting Thoughts
Probably this is not the last update on ThunderStorm since it's been my pet project for a while now. Also, considering how feeble most ciphers are when it comes to the quantum threat, someday enough people may see value in a robust and unconventional cipher, to warrant further R&D on it. Until then, it will probably remain a niche thing, much like the language it was written in, as most high-level developers prefer to stick with the languages they know instead of going for a newer and objectively better language like Julia. Cheers!
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About five months ago, I started writing a new technical book. I didn't have to, but the idea was burning me, and as I had been working on a particular data science topic the previous months, I felt it deserved to be shared with a larger audience. Of course, I could have just shared some code or perhaps put together some article, but the idea deserved more. So, I reached out to my publisher, sent him a proposal with an outline of the book, and before long, I was good to go!

During these months I had been writing regularly (pretty much daily, at least on weekdays), with just a couple of weeks off, one for the Christmas holidays and one for the preparation of my podcast. This book project involved both text, images, and code (in the form of a new type of code notebook, for Julia). So, at least, I didn't get bored, plus I was a bit imaginative with a couple of the problems I tackled in the code notebooks.

Although it's a bit soon to tell when the book will be out, at least the most time-consuming part is behind me now. Hopefully, I'll be able to focus more on other projects now. I'll keep you posted through this blog regarding updates on the book. Cheers!
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As much as I'd love to write a (probably long) post about this, I'd rather use my voice. So, if you are interested in learning more about this topic, check out the latest episode of my podcast, available on Buzzsprout and a few other places (e.g., Spotify). Cheers!
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Overview
Mentoring is one of those subjects I can talk about till the cows come home (the other such subjects are the Julia programming language, Data Science, and Cybersecurity). What makes it different, however, is that it's something that appeals to all sorts of professionals, not just data science and cybersecurity ones. In this article, I'll attempt to illustrate that through a series of questions and answers, for easier navigation and hopefully better understanding.

What?
So, first of all, what is mentoring? In a nutshell, it's the formal manifestation of the most natural relationship in our species, that of passing on knowledge. This knowledge transfer is usually done from parents to children (and vice versa when it comes to the latest apps and gadgets!), from the elders to the younger individuals, and among peers with different levels of growth in a particular field. It's the most natural thing in the world to share one's knowledge and experiences with other people, often just for the sake of it. In the business world, where time is valued differently, this relationship usually takes the form of a professional relationship where money is involved, while there is a certain structure about it (e.g., regular meetings, a preassigned means of communication, etc.)

Why?
Well, we all have blind spots and gaps in our knowledge, plus we need to learn from others (what I refer to as dynamic learning) since solitary learning strategies are sometimes inadequate. Also, mentoring is often a powerful supplement to one's established learning strategies, enabling that person to deal with practical issues and questions that often arise from the new material. It's no coincidence that anyone in academia pursuing a challenging project, such as a dissertation, is often required to have a mentor of sorts to supervise his/her work. In some cases, such as a multi-disciplinary research project, two mentors are assigned to the learner. That was my experience during my Ph.D. at the University of London.

Who?
Anyone intending to learn something or hone their skills is a candidate for a mentee/protege. As for mentors, anyone you can learn from systematically and helpfully qualifies for that role. Of course, there is also the matter of availability, since many people are quite busy these days, so that's a requirement too. Practically, you cannot be a mentee or a mentor if your schedule is jam-packed. It takes time to invest for such a relationship to have a chance, just like anything worthwhile in our lives.

How?
Mentoring usually makes use of a rhythm in the series of meetings involved. It doesn't have to be frequent, but having a rhythm is useful nevertheless. You can use the mentoring meetings to discuss
1. new topics the learner is interested in and often tackling individually,
2. problems the learner is facing, such as those related to the new material as well as its applications,
3. specific applications of the new material to understand how it applies in practice,
4. new ideas that extend the learning material and may be the product of the learner’s creativity,
5. anything else that the learner deems necessary or useful such as career-related matters

How Much?
As with any product or service out there, there is a price tag involved (be very careful when someone is offering mentoring or access to "mentors" for free, as this is likely to be a scam). In general, the more you value the mentoring process, the more you're willing to pay for it. Sometimes, you can even work out an exchange kind of deal, where you offer a product or service for the mentoring you receive. More often than not, however, there is money involved, while there is also an intermediary to handle the transactions and take care of the logistics of the process.

When?
Well, there is no better time than now, or at least, as soon as you can. Waiting for the perfect mentor or for a time when you have enough time to focus on mentoring is futile. You can always adjust your mentoring rhythm to the circumstances of your life if needed. I've had to change the weekly meetings I have with my mentees a few times because they were either dealing with a personal situation or a work-related matter.

Where?
Anywhere with a good internet connection (even a mobile internet connection) or, ideally, within proximity of the mentor. I remember having been paired with a mentor during my time in Microsoft and I've mentored people in person through the "Get Online" program in Greece, back in the day when the internet was a new thing and local business people were eager to utilize it for their businesses. However, most of the mentoring these days take place over a VoIP system, such as Zoom, or even over the phone. Generally, a VoIP system is preferable since it allows you to share your screen with the mentor and enable them to understand the problem better, facilitating a potential resolution.

So What?
All this sounds nice and dandy, but so what? The bottom line of all this is that through mentoring, you get to improve your skills (or develop new ones if you are a newcomer in a field), refine your mindset, and even upgrade your life status over time. Many people take on mentoring to shift careers or get a better job in their line of work, while others do it to become better at their current job. Every person is unique, and mentoring addresses that uniqueness, building on it.

Shameless self-promotion part
If you have been following my work or my blog, you're probably already aware of the fact that I'm involved in mentoring for several years. Lately, I've decided to take it to the next level and start mentoring people on other platforms too as well as one-on-one (no intermediary platform). Although I usually deal with the main currencies of the world (e.g., USD, British pounds, and Euros), I'm also open to cryptocurrencies too. You can learn more about my mentoring endeavors on the corresponding page of this blog. Cheers!

Alright, the new episode of my podcast, The Ethics of Analytics Work and Personally Identifiable Information, is now live! This is a fundamental one since here I try to clarify what PII is, a term that  is used extensively in most future episodes of the podcast. Also, I talk about ethics, without getting all philosophical, and describe how it’s relevant to our lives, especially as professionals. So, check it out when you have a moment! Cheers.

I was never into Sampling techniques, even though I had to code a couple of them from scratch during my Ph.D. as there was no K-fold cross-validation method in Matlab at the time. Although nowadays it seems masochistic for me to code in Matlab, I am grateful for the experience. After all, the Julia language that I use regularly is very similar to Matlab in terms of syntax so this experience with Matlab coding made the learning of Julia easier and faster. Could it be possible that we could make data summarization easy and fast too, hopefully without resorting to any closed-source software like Matlab?

This question has kept me wondering for a while now (perhaps more than I'm willing to admit!) partly because my data structures know-how wasn't there yet. Lately, however, I learned all about K-D trees, which are a more generalized form of binary search trees. I even published an article about it on the AIgents platform. In any case, K-D trees enable the quick finding of nearest neighbors as well as the filtering of data points within a given distance (I deliberately avoid saying hypersphere because if you've dealt with high-dimensional data as I've had, you probably detest that shape too!). In any case, finding points within a given distance (or radius if you are geometrically inclined) is necessary if you were to examine different areas of the dataset, particularly if you want to do that a lot. Since K-D trees make that easy and scalable, one can only wonder why no one ever thought about using them in data summarization yet.

In simple terms, data summarization is representing the information of the original dataset with fewer data points (the fewer the better). Of course, you can do that using a centrality metric of your preference but summarizing a whole dataset, or even a variable, with one point creates more problems than it solves. It's this naive approach to data summarization that has brought about all the prejudices and discriminatory behavior over the years. Nassim Taleb is also very critical of all this and that's someone who has been around more and thought about things in more depth than most of us.

Anyhow, data summarization is tricky and relatively slow. It's much easier to take a (hopefully random and unbiased) sample, right? Sure, but what if we don't want to take any chances and want to reduce the dataset optimally instead? Well, then we have no choice but to employ a data summarization method. The one I've developed recently, employing a couple of heuristics, does the trick relatively fast, plus it scales reasonably well (also, it's entirely automated, so there's no need to worry about normalization or the size of the summary dataset). Attached are the dataset I used (related to Portuguese wines) and a couple of plots, one for the first two variables of the dataset and one for the reduced version of that. The method works with K-dimensional data, but for the sake of demonstration, I only used two of them.

For all this, along with a vector for the weights of the created data points, it took around 0.4 seconds on my 5-year-old machine. The reduction rate was about 65%, which is quite decent. For the whole dataset (all 13 variables) it took a bit longer: ~ 29 seconds, with a 54% reduction rate.

Although the method seems promising, there are probably a few more optimizations that can be performed to it, to make it even more scalable. However, it’s a good start, particularly if you consider the new possibilities such a method offers. The one obvious one, which I’ve already explored, is data generation. The latter can be done independently from the data summarization part, but it works better if summarized data is used as an input. Another low-hanging fruit kind of application that's worth looking into is dimensionality reduction, based on the summarized dataset. All of these, however, is a story for another time. Cheers!
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Two weeks have passed since I launched the podcast and so far the number of downloads have exceeded my expectations (with over 2100 downloads so far).  Yet, regardless of all this, I continue humbly with my efforts to raise awareness about the whole Privacy matter and how it's relevant to Analytics work.

In the latest episode of the podcast, published just this morning, I interview Steve Hoberman, the data modeling professional and lecturer at the Columbia University I've been working with since the beginning of my career in data science. Without getting too technical, we talk about various topics related to the relationship of Analytics professionals and the Business, as well as how privacy factors in all this.  This is the only episode of this podcast that doesn't contain a sponsor ad, for obvious reasons.

Check it out when you have a moment!

​Lately, I've been preparing a podcast on the topic of (data) Analytics and Privacy. Having completed the first few episodes, I've decided to make it available at Buzzsprout. Alternatively, you can get the RSS feed to use with either a browser add-on or some specialized program that handles RSS links: https://feeds.buzzsprout.com/1930442.rss

The podcast deals with various topics related to privacy, usually from an analytics angle, or vice versa. However, it appeals to anyone who is interested in these subjects, not just specialized professionals. Clocked at around 20 minutes each, the episodes of this podcast are ideal for your daily commute or any other activity that doesn't require your full attention. 

Feel free to check out these links  and, if you like the podcast, share these links with friends and colleagues. Cheers!