anisotropyTswirl {CoSMoS} R Documentation

## Swirl anisotropy transformation

### Description

Swirl anisotropy transformation.

### Usage

```anisotropyTswirl(spacepoints, x0, y0, b, alpha)
```

### Arguments

 `spacepoints` vector of coordinates (2 x d), where d is the number of locations/grid points `x0` x coordinate of the center of the swirl deformation `y0` y coordinate of the center of the swirl deformation `b` scaling parameter controlling the swirl deformation `alpha` rotation angle

### References

Ligas, M., Banas, M., Szafarczyk, A. (2019). A method for local approximation of a planar deformation field. Reports on Geodesy and Geoinformatics, 108(1), 1-8, doi: 10.2478/rgg-2019-0007

Papalexiou, S.M., Serinaldi, F., Porcu, E. (2021). Advancing Space-Time Simulation of Random Fields: From Storms to Cyclones and Beyond. Water Resources Research, 57, e2020WR029466, doi: 10.1029/2020WR029466

### Examples

```
## specify coordinates
m = 25
aux <- seq(0, m - 1, length = m)
coord <- expand.grid(aux, aux)

at <- anisotropyTswirl(spacepoints = coord,
x0 = floor(m / 2),
y0 = floor(m / 2),
b = 10,
alpha = 1.5 * pi)

## visualize transformed coordinate system
aux = data.frame(lon = at[ ,1], lat = at[ ,2], id1 = rep(1:m, each = m), id2 = rep(1:m, m))
ggplot(aux, aes(x = lon, y = lat)) +
geom_path(aes(group = id1)) +
geom_path(aes(group = id2)) +
geom_point(col = 2) +
theme_light()
```

[Package CoSMoS version 2.1.0 Index]