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Tom West

I can't see how you can complain about a line chart here. The two variables are both continuous (time and unemployment). At a point mid-way between in time between two points, the unemployment will be (roughly) mid-way between the unemployment at those two points. So it's perfectly sensible.


It seems to me the more effective version of both these plots would be to have, in every multiple, a line representing median values for the whole set. The shapes of the curves are too similar for my eyes to judge differences between them.

Andrew Gelman

This reminds me of a conversation I had with Bill Cleveland once. He showed me some set of graphs similar to those above, and I suggested he pull out means and plot residuals. He replied that he had formerly been a big fan of such decompositions but in his recent experience had felt that, as much as possible, he preferred to plot the raw data, that much could be learned from a careful set of graphs that displayed every point in the data just as it was.

I don't know if Cleveland's idea would work so well with discrete data, but it's an interesting thought.


Andrew and Andy: I did all kinds of plots that I didn't show of the type you're thinking about. And I agree that what's hidden in this small-multiples view is the small variations from year to year. The charts here present a good illustration of stronger versus weaker effects.

In particular, a good complement to the charts above is one that collapses all the separate multiples and use year as overlay. That one allows readers to observe both the stability of the seasonal pattern plus the small year-to-year shifts. However, I think it's harder for people to grasp.

Andrew: one thing I like doing is to plot the raw data after the modeling phase. Use the model to figure out which variables are important, then do plots of the raw data focused on those variables. It's a nice model checking device to make sure that the data actually behave the way the model says they should.

Podiatrist Calgary

With data analysis such an important part of staying competitive in the business world, companies must have the tools needed in order to effectively do the job. With nothing to lose, but maybe a little time, this deal seems too good to pass up. This is worth downloading and tucking away. Useful article.


This is a good illustration of the difference between seasonality and cyclicality. Superficially they look similar here (due to the number of years), although they are conceptually much different.

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