From an sf object containing points, calculate the standard deviational ellipse.

## Arguments

- geometry
an sfc object. If a polygon, uses

`sf::st_point_on_surface()`

.

## Value

An sf object with three columns

`sx`

: major axis radius in CRS units,`sy`

: minor axis radius in CRS units,`theta`

: degree rotation of the ellipse.

sf object's geometry is the center mean point.

## Examples

```
#' # Make a grid to sample from
grd <- sf::st_make_grid(n = c(1, 1), cellsize = c(100, 100), offset = c(0,0))
# sample 100 points
pnts <- sf::st_sample(grd, 100)
std_dev_ellipse(pnts)
#> Simple feature collection with 1 feature and 3 fields
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: 52.84892 ymin: 51.07882 xmax: 52.84892 ymax: 51.07882
#> CRS: NA
#> sx sy theta geometry
#> 1 39.8631 42.98488 133.0087 POINT (52.84892 51.07882)
```