By now, you know Orange quite well. But how about if you want to do some specialized research in, say, bioinformatics or text mining? Add-ons are coming to the rescue. You can find add-ons under Options – Add-ons. This will display a package list from where you can install the add-ons you want. Say we want to go with bioinformatics. Select the package you wish to install and press OK. Now restart Orange and you will see an additional widget set on the left. Ok, let’s explore what’s in the add-on. There are some visualization widgets, some specialized data analysis techniques, and a few widgets that offer access to external databases. One such widget is GEO Data Sets that offers access to a large repository of gene expression profiles. There are a few thousands of data sets you can load from the widget. Say, I’m interested in researches on smoking. We first filter the data on this keyword. Now let’s select the small data set. This one looks nice. First, we want to see what kind of data we got. These are gene expression data for five smokers and five non-smokers. We have gene expressions in columns and samples in rows. Now we want to visualize these data to quickly check if there’s any difference between smokers and non-smokers based on their gene expression profiles. There are so many features to choose from so how do we make sense of it? Multi-dimensional scaling will help. This technique projects multi-dimensional data to a 2D space. We see there are two nice groups, blue for non-smokers and red for smokers. There is one sample from a smoker which is outlier. This could be very helpful. Even if we’re not molecular biologists we can see that smoking leaves a trace on a cellular level. But enough biology for now. Multi-dimensional scaling and other embedding techniques are a great way to understand the underlying patterns in any kind of data. We will talk more about 2D embedding in the upcoming tutorial. As for today, we have learned how to install add-ons in Orange and how to use new widgets in combination with the existing ones.