Outliers in Traffic Signs

Say I am given a collection of images of traffic signs, and would like to find which signs stick out. That is, which traffic signs look substantially different from the others. I would assume that the traffic signs are not equally important and that some were designed to be noted before the others.

I have assembled a small set of regulatory and warning traffic signs and stored the references to their images in a traffic-signs-w.tab data set.

Related: Viewing images

Related: Video on image clustering

Related: Video on image classification

The easiest way to display the images is by loading this data file with File widget and then passing the data to the Image Viewer,

Opening the Image Viewer allows me to see the images:

Note that initially the data table we have loaded contains no valuable features on which we can do any machine learning. It includes just a category of traffic sign, its name, and the link to its image.

We will use deep-network embedding to turn these images into numbers to describe them with 2048 real-valued features. Then, we will use Silhouette Plot to find which traffic signs are outliers in their own group. We would like to select these and visualize them in the Image Viewer.

Related: All I see is silhouette

Our final workflow, with selection of three biggest outliers (we used shift-click to select its corresponding silhouettes in the Silhouette Plot), is:

Isn’t this great? Turns out that traffic signs were carefully designed, such that the three outliers are indeed the signs we should never miss. It is great that we can now reconfirm this design choice by deep learning-based embedding and by using some straightforward machine learning tricks such as Silhouette Plot.

Image Analytics: Clustering

Data does not always come in a nice tabular form. It can also be a collection of text, audio recordings, video materials or even images. However, computers can only work with numbers, so for any data mining, we need to transform such unstructured data into a vector representation.

For retrieving numbers from unstructured data, Orange can use deep network embedders. We have just started to include various embedders in Orange, and for now, they are available for text and images.

Related: Video on image clustering

Here, we give an example of image embedding and show how easy is to use it in Orange. Technically, Orange would send the image to the server, where the server would push an image through a pre-trained deep neural network, like Google’s Inception v3. Deep networks were most often trained with some special purpose in mind. Inception v3, for instance, can classify images into any of 1000 image classes. We can disregard the classification, consider instead the penultimate layer of the network with 2048 nodes (numbers) and use that for image’s vector-based representation.

Let’s see this on an example.

Here we have 19 images of domestic animals. First, download the images and unzip them. Then use Import Images widget from Orange’s Image Analytics add-on and open the directory containing the images.

We can visualize images in Image Viewer widget. Here is our workflow so far, with images shown in Image Viewer:

But what do we see in a data table? Only some useless description of images (file name, the location of the file, its size, and the image width and height).

This cannot help us with machine learning. As I said before, we need numbers. To acquire numerical representation of these images, we will send the images to Image Embedding widget.

Great! Now we have the numbers we wanted. There are 2048 of them (columns n0 to n2047). From now on, we can apply all the standard machine learning techniques, say, clustering.

Let us measure the distance between these images and see which are the most similar. We used Distances widget to measure the distance. Normally, cosine distance works best for images, but you can experiment on your own. Then we passed the distance matrix to Hierarchical Clustering to visualize similar pairs in a dendrogram.

This looks very promising! All the right animals are grouped together. But I can’t see the results so well in the dendrogram. I want to see the images – with Image Viewer!

So cool! All the cow family is grouped together! Now we can click on different branches of the dendrogram and observe which animals belong to which group.

But I know what you are going to say. You are going to say I am cheating. That I intentionally selected similar images to trick you.

I will prove you wrong. I will take a new cow, say, the most famous cow in Europe – Milka cow.

This image is quite different from the other images – it doesn’t have a white background, it’s a real (yet photoshopped) photo and the cow is facing us. Will the Image Embedding find the right numerical representation for this cow?

Indeed it has. Milka is nicely put together with all the other cows.

Image analytics is such an exciting field in machine learning and now Orange is a part of it too! You need to install the Image Analytics add on and you are all set for your research!

BDTN 2016 Workshop: Introduction to Data Science

Every year BEST Ljubljana organizes BEST Days of Technology and Sciences, an event hosting a broad variety of workshops, hackathons and lectures for the students of natural sciences and technology. Introduction to Data Science, organized by our own Laboratory for Bioinformatics, was this year one of them.

Related: Intro to Data Mining for Life Scientists

The task was to teach and explain basic data mining concepts and techniques in four hours. To complete beginners. Not daunting at all…

Luckily, we had Orange at hand. First, we showed how the program works and how to easily import data into the software. We created a poll using Google Forms on the fly and imported the results from Google Sheets into Orange.

To get the first impression of our data, we used Distributions and Scatter Plot. This was just to show how to approach the construction and simple visual exploration on any new data set. Then we delved deep into the workings of classification with Classification Tree and Tree Viewer and showed how easy it is to fall into the trap of overfitting (and how to avoid it). Another topic was clustering and how to relate similar data instances to one another. Finally, we had some fun with ImageAnalytics add-on and observed whether we can detect wrongly labelled microscopy images with machine learning.

Related: Data Mining Course in Houston #2

These workshops are not only fun, but an amazing learning opportunity for us as well, as they show how our users think and how to even further improve Orange.