One problem I have with the first graph from a purely technical point of view is that the number of horizontal data points far exceeds the resolution I used for the plot. So, the data as shown has been filtered by the underlying plot routines.
Here is a plot where the data actually fits the resolution: http://www.jsoftware.com/jwiki/Scripts/WeatherPlot?action=AttachFile&do=get&target=rochester2005temp.png I'm not if either plot tells me much about a phenomenon that most likely is global and may be better analyzed on a scale of centuries. -- David Mitchell On 1/7/2010 16:14, Björn Helgason wrote: > Well your first graph looks interesting and it gives a picture of big > variation of temperatures. > So if you want to present any trend out of the data it needs to be > treated with seasonal adjustments. > > Series are made up of four components: > St: The Seasonal Component > Tt: The Trend Component > Ct: The Cyclical Component > It: The Error, or irregular component. > > One way of looking at such data is take each daily value and compare > that value with the average value for that day > > One scary thing about the discussions about heat measurements and > trends over time is that the researchers have been manipulating the > data to fit their interests. > > > > > 2010/1/7 David Mitchell<[email protected]>: >> Yes, the second data set is the minimum high and minimum low temperatures for >> yearly intervals. It is an extract from the original data. >> >> -- >> David Mitchell >> >> On 1/7/2010 13:41, Björn Helgason wrote: >>> The Y scale in one graph goes from -20 to +100 and so do the curves >>> The Y scale on the other goes from -20 to +20 and the curves therefore >>> not the same >>> >>> >>> 2010/1/7 David Mitchell<[email protected]>: >>>> It may depend on how one looks at the data: >>>> >>>> http://www.jsoftware.com/jwiki/Scripts/WeatherPlot?action=AttachFile&do=get&target=rochestermintemp.png >>>> >>>> ;) >>>> >>>> -- >>>> David Mitchell >>>> >>>> On 1/7/2010 9:23, Björn Helgason wrote: >>>>> Looking at this data it is nothing that says there is any general >>>>> warming going on. >>>>> >>>>> If anything it looks like it is getting cooler. >>>>> >>>>> >>>>> >>>>> 2010/1/6 David Mitchell<[email protected]>: >>>>>> >>>>>> Here is one example of what I find useful with J: >>>>>> >>>>>> http://www.jsoftware.com/jwiki/Scripts/WeatherPlot >>>>>> >>>>>> -- >>>>>> David Mitchell ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
