R: QQ-plot for the GEV parameters

qqgev {SpatialExtremes} | R Documentation

## QQ-plot for the GEV parameters

### Description

This function compares the GEV parameters estimated separately for each location to the ones estimated from a fitted spatial model.

### Usage

    qqgev(fitted, xlab, ylab, ...)

### Arguments

`fitted` | An object of class `maxstab` or `spatgev`. Most often, this will be the output of `fitmaxstab`, `fitcovmat`, `fitcovariance` or `fitspatgev`.
`xlab,ylab` | The x and y-axis labels. May be missing.
`...` | Optional arguments to be passed to the `plot` function.

### Value

A QQ-plot.

### Author(s)

Mathieu Ribatet

### References

Schlather, M. (2002) Models for Stationary Max-Stable Random Fields. Extremes 5:1, 33–44.

Schlather, M. and Tawn, J. A. (2003) A dependence measure for multivariate and spatial extreme values: Properties and inference. Biometrika 90(1):139–156.

Smith, R. L. (1990) Max-stable processes and spatial extremes. Unpublished manuscript.

### See Also

`qqextcoeff`

### Examples

    ##Define the coordinate of each location
    n.site <- 30
    locations <- matrix(runif(2*n.site, 0, 10), ncol = 2)
    colnames(locations) <- c("lon", "lat")

    ##Simulate a max-stable process - with unit Frechet margins
    data <- rmaxstab(50, locations, cov.mod = "gauss", cov11 = 100, cov12 =
    25, cov22 = 220)

    ##Now define the spatial model for the GEV parameters
    param.loc <- -10 + 2 * locations[,2]
    param.scale <- 5 + 2 * locations[,1] + locations[,2]^2
    param.shape <- rep(0.2, n.site)

    ##Transform the unit Frechet margins to GEV
    for (i in 1:n.site)
      data[,i] <- frech2gev(data[,i], param.loc[i], param.scale[i], param.shape[i])

    ##Define a model for the GEV margins to be fitted
    ##shape ~ 1 stands for the GEV shape parameter is constant
    ##over the region
    loc.form <- loc ~ lat
    scale.form <- scale ~ lon + I(lat^2)
    shape.form <- shape ~ 1

    fitted <- fitspatgev(data, locations, loc.form = loc.form, scale.form =
    scale.form, shape.form = shape.form)

    qqgev(fitted)

[Package SpatialExtremes version 2.0-5 Index]