Introduction I am a self confessed data sink and yesterday, for no real reason, I downloaded and worked on a data set of a thousand year old English Oak tree, living in Poland. I applied Ratio to Moving Averages to it and got myself a forecast for growth. I also applied Forecast Sheet to the data and got some forecasts from there too. My main point in writing here, however, has nothing to do with any of the above, it’s all to do with the graph I drew of a selection of tree rings of that tree. A Tree Ring Chart
There you are: a tree ring for a one year old tree, 90 year old ring, 190 years  … 990 years old. I added the diameter arrow and a text box and the table at the top is just part of my calculation and output table in the worksheet itself. How did I Draw the Graph? Actually, I just drew the graph and it turned out to be so simple, However, I searched the web for ideas on drawing a graph of a circle: several circles; and I came across some fantastic mathematical suggestions but no one as far as I can tell, has done this before for tree rings. It is easy to find examples with radar charts that draw smooth lines, along the lines of mine. I used 100 data points per tree ring to ensure as near a perfect circle as possible. The data are not mine but the licence to use them seems to suggest I am free to use and demonstrate them providing I give full credit to the source: of course I am happy to do that and I give full credit with links to 
Tomasz Wazny in the Excel file that you can download from the link below.

Other Things to do

You should look carefully at my file since it contains a myriad things to do:
  • Ratio to Moving Average Method
  • Forecast Sheet for Forecasting
  • Descriptive Statistics
  • Histogram and Box & Whisker Plot
  • Derivation of Circumference (Girth)
  • Curve Fitting of Oak Tree Age Estimator to give y = 0.001x^2 – 0.0125x + 42.029
  • Pivot Tables and Pivot Charts showing Grouped Data

Conclusions

I do not know the scale of the data set so I assumed centimetres. However, at year 990 that assumption gave me a tree with a diameter of just 10 metres and by the formula I derived for age estimation, such a tree is only 135 years old. I am trying to find out what the units of measurement are. Otherwise, I enjoyed learning a little bit more about tree rings and I was very pleased to think about using a Radar Chart to represent the tree rings themselves. Download Excel file … Duncan Williamson 2nd November 2018
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