Under the two-plane parametrization, when we fix one spatial dimension and one angular dimension (x*,u*) (or (y*, v*)), the EPI appears.
Ghasemi and Vetterli  proposed to extract energy feature vector based on the change of gradient of EPI and to distinguish the flat surface from nonflat one by using a Bayes classifier.
It is well observed that, for a flat surface which is parallel to the camera plane, all epipolar lines in the EPI have the same slope since they are in the same depth.
When the point is in an EPI with a fixed [y.sup.*], its depth can be expressed by a linear function only on x (Figure 1),
The mathematics of the Gordon model, that is, dividing the last monthly EPI by the earliest monthly EPI then deducting 1 from the quotient is the shortcut used to compute for the growth rate for 2006-2017.
When the (2006=100) series was discontinued after June, the EPI growing average is 139.78 for 2018, based on Table V below.
The mean EPI (2006=100) forecast for December 2018 is 144.22.
Using all the 88 rebased EPI values appearing on the PSA website as (2012=100), the mean EPI forecast generated for December 2018 is 102.98.