21 January 2011

Wrestling with data

I'll suggest those who haven't been, join me in keeping an eye on a series of posts that Ron Broberg is doing over at The Whiteboard.  As befits a whiteboard, he's showing a lot of the details that get cleaned out of most final publications, even on blogs.  The topic at hand is looking at the temperature records since 1880 and testing ideas on fitting curves to the data.  The series is now to #9 and it's apparent that there will be several more:

http://rhinohide.wordpress.com/2011/01/07/lines-sines-and-curve-fitting-1-oh-my/ (Starts out more on the issue of testing ideas on what we can conclude about temperature trends)
http://rhinohide.wordpress.com/2011/01/08/lines-sines-and-curve-fitting-2-r/ (try fitting the sine and then a line)
http://rhinohide.wordpress.com/2011/01/09/lines-sines-and-curve-fitting-3-double-down/ (Try fitting 2 sine waves)
http://rhinohide.wordpress.com/2011/01/10/lines-sines-and-curve-fittings-4-walk-and-chew-gum/ (Simultaneous line and sine fit.)
http://rhinohide.wordpress.com/2011/01/12/lines-sines-and-curve-fitting-5-a-growth/ (Trying an exponential curve)

http://rhinohide.wordpress.com/2011/01/15/lines-sines-and-curve-fitting-7-normal/  (Testing Normality 1)
http://rhinohide.wordpress.com/2011/01/16/lines-sines-and-curve-fitting-8-dagostino/ (Testing Normality 2)

A sine is a standard oscillation.  It would be a pure tone (rather flute-like) in music.  For a bit more about oscillations and data series, and the language of time series analysis, take a look at my Introduction to Time Series Analysis.


Ron Broberg said...

Feel free to help that poor blogger along with a kick in the rear or a hint of an overlooked passageway.

What I'm doing is exploration. I'll be grateful for a nudge or two if I track the wrong way.


Penguindreams said...

You've been doing fine Ron. A couple of times you initially didn't do something that I would have done, but a post or two later in your exploration you hit it.

I think that's one of the useful points. It is exploration -- trying to come to understanding of the data. And explorations don't really have a simple checklist of things to follow, or in what order. You just start with some data and work towards an understanding -- could there be a trend in it? Could there be a sine wave? Is the trend more likely linear, exponential, ...?

You mention fourier analysis at one point. I don't know how R does for that, but some software I like for it is http://www.lsce.cnrs-gif.fr/ -- AnalySeries.