Adding Colour to Graphs
A really important part of data visualisation (and exploration) is the use of colour to identify features. iNZight allows users to quickly and easily add colour to a graph to explore new, more complex relationships within the data.
This example uses the Gapminder example dataset in iNZight. Go to File > Load Example Data and choose "gapminder" from the Dataset dropdown.
Scatter plots with colour
The easiest way to demonstrate the awesome capability of colour in graphics is with a scatter plot. We're going to replicate part of the famous example by Hans Rosling using the Gapminder data.
To begin, we'll create a scatter plot of life expectancy by average income, and then subset using year (categorical):
// TODO: FIGURE
Not sure which variables to use?
You should have the following variables in the control panel:
Variable 1: LifeExpectancy
Variable 2: IncomePerPerson
Subset Variable 1: Year_cat
Often when you're looking at data, the values of some variables might be heavily skewed. In the example above, Income per person is right skewed because most countries have low incomes, but a handful have very large ones. If you come across this in your exploration, there's a handy mathematical "trick" that usually works (if doesn't work if some of the values are negative or zero, however): the log transformation.
You can apply a log transformation to a variable in iNZight by opening the Add to Plot window (see below), and from the top dropdown choose Axes and labels. Then simply tick the box next to the variable you want to apply a log transformation to (here, IncomePerPerson).
// TODO: FIGURE
The last step before adding some colour is to drag the slider for the Year subset across to a single year (in this example we have chosen 1972 for no particular reason). You will see the life expectancy by average income for all countries in 1972. You can see the general trend---higher income is associated with longer lives---but it would be good if we could see some kind of geographical pattern.
// TODO: FIGURE
We are going to use colour to see how things vary between regions of the world (America, Europe, Asia, etc.). To do this, click the Add to Plot button in the plot toolbar (in the bottom-left of the iNZight window). In the figure above, the icon is indicated by a red box.
The panel that opens up is called the Add to Plot panel, and it provides you with a lot of new functionality. For now, we are only interested in the Colour section, particularly the drop-down box labelled Colour points by. This does exactly what you expect---it lets you choose a variable from the drop down and iNZight will automatically colour all of the points using that variable! Go ahead and choose Region from the dropdown. Here's what you should see:
// TODO: FIGURE
Congratulations! You've created a scatter plot coloured by region. Note how the countries within regions tend to be clumped together? We'll learn how to explore this further later, for now we'll check out one last trick.
While you in the Add to Plot panel, feel free to try some other variables in the Colour by drop down. Can you find any interesting relationships?
Adding motion
Remember the play button from the last section? Close the Add to Plot button by clicking the Home button at the bottom (if you haven't already). Now, beside the slider for Year you'll see a blue play button (triangle). Click it!
Other Add to Plot features
You can do a lot of things from the Add to Plot panel, including changing colour, size, and shape of points. There are some details on each of these in dedicated documentation pages, but for now you might like to explore them. Not sure what something does? Click it and find out!