vg_calc: Perform variogram analysis on 'bfastSpatial()' shift and...
In jnghiem/bfasttools: Tools for BFAST spatial analysis

Description Usage Arguments Details Value Examples

This function uses the gstat package to compute variogram statistic for the shift and slope output from bfastSpatial output. This function uses the exponential variogram model.

1 2	vg_calc(bfast_in, boundary = NULL, template, cutoff_dist = NULL, mc.cores = 6)

`bfast_in`	A data frame generated by `bfastSpatial()`.
`boundary`	A SpatialPolygons object defining the boundary of the variogram analysis. If this argument is not supplied, all records in `bfast_in` will be used.
`template`	A Raster object with the same resolution, extent, and projection as the raster dataset used to generate `bfast_in`. Alternatively, an XML file generated by `create_raster_metadata()`.
`cutoff_dist`	An optional data frame containing the output of `pcf_calc()` for the same study area.
`mc.cores`	A numeric indicating the number of cores to be used in parallel computing.

This function returns a data frame with the following fields:

year: The year of the observation.
month: The month of the observations.
stat: The BFAST statistics ("slope" or "shift")
model: The variogram model ("Nug" or "Exp")
psill: The partial sill.
range: The range parameter of the model. Only valid for Exp model.
effective_range: The effective range of the model (within 5 sill). Only valid for Exp model.
SSerr: The sum of squared errors of the model from the sample variogram.
n: The number of points in the sample variogram.

If the variogram model is singular or does not converge after 200 iterations, no model is fit and NAs are returned for the entire row. Since this function tries to fit a large number of models, it may fail to fit a substantial proportion of models if the sample variograms do not match the model well (or require transformation).

A data frame with variogram results.

## Not run: 
vg_calc(bf_df, boundary=rgdal::readOGR(dsn="C:/Desktop/shapefiles", layer="Mojave"), template="C:/Desktop/raster_metadata.xml", cutoff_dist=pcf_results, mc.cores=6)

## End(Not run)