Creates a plot sample on a regular grid with a random start location.

## Arguments

- spdf
A

`SpatialPointsDataFrame`

defining the points that are to be sampled by the plot sample.- boundary
A

`SpatialPolygonsDataFrame`

defining the survey boundary within which the points occur.- x.ppn
The proportion of the x=axis that is to be included in the plots.

- y.ppn
The proportion of the y=axis that is to be included in the plots.

- nx
The number of plots in the x-dimension.

- ny
The number of plots in the y-dimension.

## Value

A list with three components:

`plots`

:A

`SpatialPolygonsDataFrame`

object containing the plots that were sampled.`dets`

:A

`SpatialPointsDataFrame`

object containing the locations of the points within the plots.`counts`

:A

`dataframe`

containing the following columns`x`

:The x-coordinates of the centres of the plots within the boundary.

`y`

:The y-coordinates of the centres of the plots within the boundary.

`n`

:The numbers of points in each plot.

`area`

:The areas of the plots within the boundary

.

## Examples

```
# \donttest{
# Some features require the raster package
if (bru_safe_sp() &&
require("sp") &&
require("raster", quietly = TRUE) &&
require("ggplot2", quietly = TRUE)) {
data(gorillas, package = "inlabru")
plotpts <- plotsample(gorillas$nests, gorillas$boundary,
x.ppn = 0.4, y.ppn = 0.4, nx = 5, ny = 5
)
ggplot() +
gg(plotpts$plots) +
gg(plotpts$dets, pch = "+", cex = 2) +
gg(gorillas$boundary)
}
# }
```