Log Scales

I’m learning at long last how changing scales can expose patterns. Today I’ve been looking at the Facebook Page of Marks & Spencer (a UK retailer.)

Using a linear scale on the y-axis, we see how engagement has increased rapidly over recent months. That’s pretty much text book stuff for a well-run Page.

Marks linear

But by dropping a log2(x) scale onto the y-axis (why log 2? I was experimenting after reading When Should I Use Logarithmic Scales in My Charts and Graphs?) we can see a couple of strange patterns emerging.

Marks log 2

Notice the distinct vertical lines around October and December 2011, and again in February 2012? Also the horizontal lines that extend from around January to April 2012?

Both can — it turns out — be explained by odd posting behaviour related to photo albums; and could raise some interesting issues of what is and what isn’t best practice.

But the short point is; I wouldn’t have seen it but for the log scale.

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