**Note**: this is not a serious blog post.

Neil Hall’s think piece in Genome Biology on the Kardashian index (K-index) caused an online storm recently, spawning hashtags and outrage in not-so-equal measure. Despite all the vitriol that headed Neil’s way, very little of it concerned his use of Microsoft Excel to make his plot of Twitter followers vs total citations! Looking at the plot with the ellipse around a bunch of the points and also at the equations, I thought it might be worth double-checking Neil’s calculations.

In case you don’t know what this is about: the K-index is the ratio of actual Twitter followers (\(F_{a}\)) to the number of Twitter followers you are predicted to have (\(F_{c}\)) based on the total number of citations to your papers (\(C\)) from the equation:

\(F_{c}=43.3C^{0.32} \)

So the K-index is:

\(K-index=\frac{F_{a}}{F_{c}}\)

He argues that if a scientist has a K-index >5 then they are more famous for their twitterings than for their science. This was the most controversial aspect of the piece. It wasn’t clear whether he meant that highly cited scientists should get tweeting or that top-tweeters should try to generate some more citations (not as easy as it sounds). The equation for \(F_{c}\) was a bit suspect, derived from some kind of fit through some of the points. Anyway, it seemed to me that the ellipse containing the Kardashians didn’t look right.

I generated the data for \(F_{c}\) and for a line to show the threshold at which one becomes a Kardashian (k) in IgorPro as follows:

`Make /o /N=100000 fc`

fc =43.3*(x^0.32)

Duplicate fc k //yes, this does look rude

k *=5

display fc, k //and again!

This plot could be resized and overlaid on Neil’s Excel chart from Genome Biology. I kept the points but deleted the rest and then made this graph.

The Kardashians are in the peach zone. You’ll notice one poor chap is classed as a Kardashian by Neil, yet he is innocent! Clearly below the line, i.e. K-index <5.

Two confessions:

- My K-index today is 1.97 according to Twitter and Google Scholar.
- Embarrassingly, I didn’t know of the business person who gave her name to the K-index was until reading Neil’s article and the ensuing discussion. So I did learn something from this!

—

The post title is taken from “Vitamin K” by Gruff Rhys from the Hotel Shampoo album.

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