In the previous video, I've shown you how we can use the principles and some of the notions that I've introduced in this lesson to criticize and also redesign an existing graph. Now, I want to give you another example where we are starting from some data set and a question. You don't have an existing graph, you just have to solve the problem of how to design or use the right visual representation for the problem that you have, which is one of the most common situations for visualization designers. Right? So, you have a goal, you have a data set, you want to answer some questions, and you want to create an appropriate graph. Okay. For this example, I'm using data coming from the restaurant inspections data that I've used in previous examples as well. Let me tell you again what this data is about. So there are food inspections in New York City. Every single item is a restaurant, and an inspection. And for every inspection, the restaurants receive a grade or a score. Now, let's say that one of the main questions that we have while we are analyzing this data is which cuisine type has the best distribution of grades. And we have four or five different cuisine types, and we have four or five different grades. We want to visually compare them so that we can say, this cuisine type is a much better distribution in terms of grades than this other one. How do I do that? What's the best visual representation for doing that? Let me show you three possible representations, and then reason about why one should be better than the others. Here are the three representations that I've chosen and designed. The first one on the top left is a table or a matrix. What you see is that in columns, you have five different cuisine types, and in rows you have the possible grades: A, B, C, and so on. And I mapped the percentage of the grades on the size of these rectangles. The one at the bottom uses a different design, uses pie charts. So I have one pie chart for every single cuisine type. And the segments within the pie charts are actually the proportions of the grades. And the final one is a bar chart, it's actually a set of bar charts, multiple bar charts where I think we also called these group bar chart in the previous lessons. And every single group represents one cuisine type, and every bar represents the percentage for that grade for that cuisine type. Now, as you can see, when we want to compare the values, comparing the value using the bar chart is way easier than in the other charts. Try to focus on a couple of bars, and try to see which one is bigger and how much bigger it is. It's so much easier to do with the bar chart compared to the other charts. Why is that? Well, it's because of the ranking of visual channels that I've shown you in the previous videos. We know that some channels are more effective than others at communicating quantitative information. So when we want to compare quantities visually, when this is the main task and the main goal, position is much better than area size and angle. And that's the reason why this graph, the one on the top right tends to be better for this specific type of task.
