lines.variomodel {geoR} | R Documentation

## Adds a Line with a Variogram Model to a Variogram Plot

### Description

This function adds a line with a variogram model specifyed by the user to a current variogram plot. The variogram is specifyed either by passing a list with values for the variogram elements or using each argument in the function.

### Usage

    lines.variomodel(x, ...)
    ## Default S3 method:
    lines.variomodel(x, cov.model, cov.pars, nugget, kappa,
                              max.dist, scaled = FALSE, ...)

### Arguments

`x` | a list with the values for the following components: `cov.model`, `cov.pars`, `nugget`, `kappa` , `max.dist`; or a numeric vector with x-axis values for the variogram. This argument is not required if the other arguments in the function are provided, otherwise is compulsory. If a list is provided the arguments which match the list elements are ignored.
`cov.model` | a string with the type of the variogram function. See documentation of `cov.spatial` for further details.
`cov.pars` | a vector or matrix with the values for the sill (sigmasq) and range (phi) parameters.
`nugget` | a scalar with the value of the nugget (tausq) parameter.
`kappa` | a scalar with the value of the smoothness (kappa) parameters. Only required if `cov.model` is one of the following: `"matern"`, `"powered.exponential"`, `"cauchy"` and `"gneiting.matern"`
`max.dist` | maximum distance (x-axis) to compute and draw the line representing the variogram model. If a list is provided in `x` the default is the distance given by `x$max.dist`. If a vector is provided in `x` it takes `max(x)`.
`scaled` | logical. If `TRUE` the total sill in the plot is equals to 1.
`...` | arguments to be passed to the function `curve`.

### Details

Adds a line with a variogram model to a plot. In conjuction with `plot.variogram` can be used for instance to compare sample variograms against fitted models returned by `variofit` and/or `likfit`.

### Value

A line with a variogram model is added to a plot on the current graphics device. No values are returned.

### Author(s)

Paulo Justiniano Ribeiro Jr. Paulo.Ribeiro@est.ufpr.br,
Peter J. Diggle p.diggle@lancaster.ac.uk.

### References

Further information on the package geoR can be found at:
http://www.est.ufpr.br/geoR.

### See Also

`lines.variomodel.krige.bayes`, `lines.variomodel.grf`, `lines.variomodel.variofit`, `lines.variomodel.likGRF`, `plot.variogram`, `lines.variogram`, `variofit`, `likfit`, `curve`.

### Examples

    data(s100)
    # computing and ploting empirical variogram
    vario <- variog(s100, max.dist = 1)
    plot(vario)
    # estimating parameters by weighted least squares
    vario.wls <- variofit(vario, ini = c(1, .3), fix.nugget = TRUE)
    # adding fitted model to the plot
    lines(vario.wls)
    #
    # Ploting different variogram models
    plot(0:1, 0:1, type="n")
    lines.variomodel(cov.model = "exp", cov.pars = c(.7, .25), nug = 0.3, max.dist = 1)
    # an alternative way to do this is:
    my.model <- list(cov.model = "exp", cov.pars = c(.7, .25), nugget = 0.3,
    max.dist = 1)
    lines.variomodel(my.model, lwd = 2)
    # now adding another model
    lines.variomodel(cov.m = "mat", cov.p = c(.7, .25), nug = 0.3,
                     max.dist = 1, kappa = 1, lty = 2)
    # adding the so-called "nested" models
    # two exponential structures
    lines.variomodel(seq(0,1,l=101), cov.model="exp",
                     cov.pars=rbind(c(0.6,0.15),c(0.4,0.25)), nug=0, col=2)
    ## exponential and spherical structures
    lines.variomodel(seq(0,1,l=101), cov.model=c("exp", "sph"),
                     cov.pars=rbind(c(0.6,0.15), c(0.4,0.75)), nug=0, col=3)

[Package geoR version 1.5-7 Index]