Heat maps
Since heat maps encode color on a continuous scale, they are difficult to accurately decode, a topic we discussed in the first course. Hence, heat maps are most useful if you have a small number of boxes and/or a clear pattern that allows you to overcome decoding difficulties.
To produce them, map two categorical variables onto the x and y aesthetics, along with a continuous variable onto fill. The geom_tile() layer adds the boxes.
We'll produce the heat map we saw in the video (in the viewer) with the built-in barley dataset. The barley dataset is in the lattice package and has already been loaded for you. Use str() to explore the structure.
This exercise is part of the course
Intermediate Data Visualization with ggplot2
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# Using barley, plot variety vs. year, filled by yield
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# Add a tile geom
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