Description Peter Robinson 2007-10-31 07:29:49 EDT

Created attachment 81705 [details]
Chart showing regression lines

Provide a way of calculating regression parameters and from that generating regression values in a dataset or a table, and also regression lines on a chart.

Requirement is to take a set of data and calculate the linear regression from that data, giving m and b parameters for the line Y=mX+b that fits the data. The regression result r-squared gives a measure of how well the calculated line fits the actual data.

When calculating the regression, some options are normally useful:
1. use either all points in the data, some selected/sampled set of the data, or the last n points.
2. optionally extending the trend past the end of the given data samples a number of cycles. Eg when looking at Daily samples of data, generate the trend a given number of days into the future.
3. optionally include some percentage growth factor(s) to be applied at given point(s) in the future trend.

For a good example see the Linear regression section here:
http://en.wikipedia.org/wiki/Regression_analysis

See attached chart with two regression lines. One regression based on all data, and the second based on just the last 3 data points. Both lines extended 3 periods past the data end. In both cases r-squared is calculated based on the correlation of the whole set of data to the trend line. This can also be calculated as a correlation between just the selected data and the resultant trend line. Both are useful and perhaps both could be provided.