Ever felt stucked on a problem?

Not a daily life problem but one about data. Maybe you’re a data scientist and your daily life problems are about data.

Often, when you struggle with this kind of problem, the issue raise in expressing it to people and the solution pops out like magic. Unfortunately, sometimes, the discussion remains sterile and you can only focus on the way you’re already reasoning. This makes some sense as somebody often surround hisself with people thinking and reasoning like his. This makes oneself feel more comfortable. The thing is that is useless when one will to think differently. So if you don’t have a weirdo friend around to get you out of a box, why not using a DeepLearning black box, untangle it to find some creativity? Sounds a little blurry? Let me explain.

Once upon a time a colleague of mine tried to solve a problem using a complex algorithm having several parameters. In fact, she solved the problem but only for a specific case. Then she realised that in order to use her algorithm in various conditions, she will have to define a large amount of values for different cases. Even then, she wouldn’t address some specific use-cases. She was struggling with a generalization problem. An other issue my friend had was that for some cases she was playing on some parameters of her algorithm and in some others she was playing on others.

Let’s take an example. Imagine you want to characterise the movement of a ball. Just a regular movement let say I am playing with my colleague and we are throwing the ball at each other. To characterize it the only needed parameter is velocity. This is what my colleague did. Now, imagine that I ain’t told her that I did 15 years of basketball reaching a certain level and I wan to play her a trick by modulating ball’s velocity and adding some effect to it. Linear velocity will not be sufficient and maybe angular velocity will be needed. So in some cases, resolving the equation is “simple” in some others, it necessitate more expertise and time.

Let’s come back to our problem. Here there is not 2 but 12 parameters and testing all the different parameter combinations and their proper value would take a lifetime. Then two ideas raised and they both involve AI but in a very different way.

The first one is quite classical. Indeed, if a human is able to find all the parameters for different conditions, so why not an AI? Giving the model time series data and associated parameters used, then training the model to find the desired parameter in any other condition. Then we could open the “black box” and try to read the feature extraction inside. This could work but the problem is that we’ve been orienting the trainig by doing the labelling. Thus we might have introduced a bias linked to the way we’ve been classifying them. During my years doing research, I’ve been tracking biases linked to the protocol desing and subjects selection or even the way we were running the experiment. Then I came to industry and at some point started to track results. Lately, I met Aurélie Jean and red her book “The other side of the mirror” (“De l’autre côté du mirroir” in French). This was a good reminder of how much space biases can take into data analysis and that both in research and industry we shoud be focusing more on data cleaning, balancing and understanding.Moreover, thinking about it, the original problem was less about finding the proper values of the parameters than finding the proper parameter to use in order to generalize a solution.

To do so, we were too much into the unperfect solution we already found, we were having blinkers and eventhough knowing it, it was really hard to make a move on any other direction unless being helped by some weirdo “friend” thinking differently than us. This friend is called unsupervised learning. Using this kind of learning one can train an algorithm to find differences on our different data but with no a priori. Thus the model will extract features in a way even (and I would say particularly) a very specialized data scientist woudn’t have. This  way, untangling the black box of feature extraction could have the same effect than a coffee conversation with one of your colleague: open your eyes to a new scope of possible. The difference here is that the machine will bring a possible solution but with no explanation and us, as human beings, needs to understand the reasoning behind the theory. Free to us though to build the story around the data and shall the data scientist’s expertise help us to explain what we were not able to see at first.

There is, to my opinion of course, a beautiful way to use deep learning. This way pushes our creativity, helps us opening our minds to a new way of solving problems by eliminating our a priori (biases) about data. In this example, opening the “black box” of deep learning was the purpose of the exercise but most of the time, the result doesn’t lay in the feature extraction but in the proper result of the model. Then one should question hisself about the input data, the model’s architecture and result. Lastly, one should look at what’s inside the model in order to be able to understand the reasoning behind the solution and not apply it blindly.