Data Viz Done Right

August 19, 2009

A-Rod's Projections

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Scott Raab wrote a fantastic article in Esquire in February when the allegations came out about A-Rod taking steroids in 2003 (and who knows how long before or after). In the article, Scott references a chart published by Esquire in October 2008 that projects A-Rod's stats and when he's projected to pass significant milestones.

There are some fundamental flaws with this chart:
(1) The vertical axis starts around 400 instead of zero; this distorts the chart (In fact, when you start the axis at 0, runs scored and RBI are nearly identical. This chart makes it look like there is a variance worth noting.)
(2) The colored background is unnecessary and distracting; keep it transparent so that the data stands out on its own
(3) The markers at each point are not needed; they take away from the natural trend of the data
(4) The total should be labeled 2018, not total

There are also a few details that make the chart work:
(1) Identifying the major milestones
(2) Labeling the projected totals
(3) The color choice is good; the colors are discernible and no one color sticks out more than another (though the red could be slightly softer)

Given the notes above, here is how I would present the data:

Good news for A-Rod, his projected stats are even better than when Scott Boras presented the data for the first graph to the Texas Rangers back in 2001. Bad news for Boras, the $252M contract you negotiated could have been higher if you presented your data more accurately (along with the 5% commission you lost).

August 18, 2009

Do oil prices have a direct correlation to the price of gold?

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I recently read an article in Forbes about tracking oil prices. The theory is that oil prices have a direct correlation to the price of gold. Therefore most of the oil increase is a result of dollar inflation, not supply and demand.

What struck me immediately is the use of the scale to artificially highlight the correlation, a big no no in data visualization. Wanting to test the theory myself, I gathered the data and used Tableau to analyze it. As the article said, there is a strong positive correlation between the prices of gold and oil. Since the price of gold is typically ahead of the price of oil, I wonder if futures traders use this to set the price of oil or at least predict its direction.

As another interesting note, but not a surprising one, oil and gold prices can be correlated pretty strongly vs the consumer price index, which is a measure of inflation.

Download the workbook with the data behind this visualization. Create your own visualizations with Tableau Desktop. Or use free Reader to filter, view and interact with the visualizations.

August 17, 2009

Pie Chart Abuse

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I ran across this post from the Replacement Level Yankees Weblog and it provided me with a fantastic example of a pie chart gone wild (aka chart junk).

Answer this question for me by looking at the pie chart: Which player had the 5th most RBIs?

Pie charts are designed to represent parts of a whole. Does this chart present the data this way? Well, I suppose it does, but is it done effectively? Certainly not. It appears the data is sorted in alphabetical order, but that doesn't provide any insight. If insisting on a pie chart, why not sort it descending by % of total RBI? Pie charts should be used sparingly, if ever. A simple bar graph displays the data much more effectively.

Answer this question for me again by looking at the bar chart below: Which player had the 5th most RBIs? Which chart made it easier to find the answer?