Update: Smoothing Jack Kirby with R

As described in a previous post, I had made a chart of Jack Kirby’s career as a comics artist. The finished product looked like this:

After thinking about it for a while I decided that I want to make some changes. First of all I want to indicate on the chart that Kirby no longer made his living from comics after 1980 (he moved into animation work). Second, maybe a straightforward connect-the-points line graph wasn’t such a great idea. The line spikes up and down a lot, making it difficult to see an overall trend. Instead, I think I want to plot the points and add a trend line using ggplot’s statistical smoothing function.

Step one: indicating Kirby’s retirement. I need to type the information for that into R.

jkhighlight <- data.frame(list(start=c(1943,1961,1980),end=c(1945,1970,1995),
period=c("Military service","The Marvel Age","Retirement")))
jkhighlight$period <- factor(jkhighlight$period, 
levels=c("Military service","The Marvel Age","Retirement"))

(The last two lines above are to reorder the ‘period’ element so it’ll appear in chronological order in the key. Otherwise, the default is to alphabetical order: WWII, then retirement, then Marvel.)

Now to replot everything as points.

ggplot(yrtotals, aes(x=year,y=pages)) + geom_point()

This gives us:

This doesn’t tell a very clear story, which is why I’m going to need the trend line. Before getting to that, let’s get rid of the grey background, clean up the axes and add a title.

last_plot() + theme_bw()
last_plot() + scale_y_continuous("Published comic art pages per year") + 
scale_x_continuous("Source: marvelmasterworks.com", breaks=seq(from=1940,to=1995,by=5)) 
+ opts(axis.title.x = theme_text(hjust=1, vjust=0, size=8), title="Jack 
Kirby's career in comics", plot.title=theme_text(hjust=0.5, vjust=1, 

And add the colour regions:

last_plot() + geom_rect(aes(NULL, NULL, 
xmin=start, xmax=end, fill=as.factor(period)), ymin=0, ymax=1300, 
data=jkhighlight, alpha=0.3) + scale_fill_manual("", values=c("red", 

Now we have:

Still not very obvious what’s actually going on here. So now it’s time to add the trend line.

last_plot() + coord_cartesian(ylim=c(0,1300),xlim=c(1937,1995))
last_plot() + stat_smooth(span=0.16)

I’m much happier with the way the graph looks now.


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