(This Post is part of my 30 day Data Visualization Challenge – you can follow along using the ‘challenge’ tag!)

I am seriously spending a lot of time thinking about diamonds, you guys. One thing that I’ve asked myself is about value – or rather, price. Are there reliable ways to tell if a particular diamond will be more expensive? Are there certain clarities or colors with more outliers or deviations in general? Looking at you, J. Here’s one way to answer that question, by looking into price per carat mapped against carat weight, split up between clarities:

Thoughts:
– We can see that even though the leftmost diamonds tend to be the largest, the price per carat paid per carat for them stays roughly equal as they increase in size.
– We can also see that as we progress to the right, there are fewer diamonds per set (probably, the dot density is a problem here), but the cost per carat climbs skyward, peaking at almost four times per carat compared to the leftmost clarity.
– This doesn’t do a great job of representing deviation from the norm, though. There is probably a better way to represent that visually.

Code:

> library(ggplot2)
> qplot(carat, price/carat, data=diamonds, alpha=I(.25)) + facet_grid(. ~ clarity) 

• Work