reports & cases
reports & cases
(1) - An amplification application of the SegReg program software permitting expression of preference for a certain type of segmentation, or of the wish to exclude a certain type, can be downloaded from SegRegA. It also gives the option to select an S-curve or a generalized third degree polynoom, see: S-curves or cubic.
(2) - A different version of SegReg, called PartReg has been developed with the aim to detect the largest possible horizontal stretch in Type 3 and Type 4 relations. This has been done to find the maximum tolerance (or "no effect" reach of the dependent variable - e.g. crop yield - for changes in the dependent variable (e.g. soil salinity or depth of the water table).
Download PartReg with this link
See the figures below to appreciate the difference between SegReg and PartReg. The first minimizes the deviations of the model values from the observed ones over the entire domain, whereas the second calculates the maximum part (range) of the domain over which the regression coefficient (i.e. the slope of the regression line) can be taken equal to zero.
For more examples see this segmented regression article on page 13 and following, the tolerance paper on soil salinity tolerance of crops, or the sensitivity paper on sensitivity of crops to shallow watertables.
Introduction screen SegReg calculator program:
The model comes with various explanations like programmed function types, calculation methods, and application of significance tests.
Example Type 3:
The SegReg model is designed for segmented (piecewise) linear regression
with breakpoint (threshold).
The application program can be used for salt tolerance of crops or the tolerance
to shallow watertables.
The software clarifies the crop response and demonstrates the resistance to
high soil salinity or water level.
This Type 3 is similar to the Maas-Hoffman model.
Example Type 3 with extended horizontal line using
the same data as above in the PartReg software application.
instead of SegReg.
According to this software model, the salt tolerance of mustard is
almost ECe=8 dS/m. After this threshold the yield reduces.
In other words, form this application program it can be deduced
that the crop resists salinity up to 8 dS/m while up to
8 dS/m there is no negative effect.
Example Type 4:
The crop tolerates a depth of the water table of 7 dm.
The Segreg software program is an application (app) made to detect different segmented models, like Type 4 in the above figure.
This type is an inverted Type 3 or an inverted Maas-Hoffman model
Example Type 5:
In year 9 (1976) a dam was contstructed in the river
The Segreg application (app) is software made to program different segmented models, for example Type 5 in the figure.