Charting annual variation

Hi there,

I am looking to chart a variable which peaks and troughs consistently through the year, just like rainfall i.e. with a high, low and mean value for each month.

I can easily chart this in Excel and Medcalc but I would like to show a polynomial trend line connecting jan-dec, effectively "wrapping" the chart as, no guessing (D'uh), January usually follows December. I don't need to compare year on year, just a smooth rolling trendline would do.

I can "cheat" by simply adding six-months data before and after but then the chart is twice as wide as it needs to be.

Does anyone know of a way to do this?

Thanks for all the help,

You mights consider using a radar or "spider" chart--I think it's called radar in Excel. The observations are spaced out at equal angles around a circle, and the value is represented by the distance from the center. If you imagine it as a clock with 12:00 as January, 1:00 is February, and so on until 11:00 is December, followed again by January. You can add multiple series(the high, low, and mean values you mentioned) and you can also add axes that give the viewer more than just a relative sense of distance from the origin.

If you're not limited to Excel and have some basic graphic design ability, you could probably just attach the bars from a normal bar chart to the outside of a small circle. It'd be the same idea, but would probably look better than Excel's radar charts.

I hope this helps.