The data were split into two halves. A copy of the first half was reversed and inverted and then attached to the front of the original data. A copy of the second half was reversed and inverted and then attached to the back of the original data. A trend line from the first data point to the last data point was subtracted from this new data set. Reversal of the first or second half of data is a procedure by which the first data point becomes the last data point of the segment, the second data point become the second to last etc.
Inversion is a procedure that flips the magnitudes about a pivot point.
The pivot point is the point closest in proximity to the original data. Figure 2 shows a schematic diagram of the data after the front and back segments are added and before the trend line is subtracted. Step 2 insures continuity at the start of the original data set. Step 3 insures continuity at the end of the original data set. Step 4 removes this gap by calculating the difference between the trend line and each data point.