R: Create a full grid from a set of coordinates

resample_grid {Morphoscape}

R Documentation

Create a full grid from a set of coordinates

Description

resample_grid() creates a rectangular grid around supplied coordinates by resampling evenly spaced points between the minimum and maximum values of each coordinate dimension. The grid can optionally be reduced to a convex or concave hull around the supplied coordinates.

Usage

resample_grid(coords2D, resample = 100, padding = 1.2, hull = NULL, alpha = 1, 
  plot = FALSE)

Arguments

`coords2D`	a 2-column matrix data frame of coordinates with the x-coordinates in the first column and the y-coordinates in the second column. The ranges of each column will be used to create the resampled grid.
`resample`	the number of points (or pixels) in the x and y dimensions over which to create the grid. Default is 100 for a kriged surface of 100x100=10,000 pixels.
`padding`	a number representing how much to expand the grid beyond the ranges of the x- and y-coordinates. For example, `padding = 1.2` (the default) expands the grid by 20% of the coordinates' ranges in each direction. Must be a number greater than or equal to 1. Large numbers imply greater extrapolation, and whatever padding is added will be negated if `hull` is specified.
`hull`	method to restrict the grid to an alpha hull using `alphahull]` or `concaveman` packages. Default is 'NULL' and no hull will be calculated.
`alpha`	when `hull != NULL`, the alpha value used to create the hull. Passed to `ahull` or `concaveman`.
`plot`	Logical. When `hull` is specified, whether to plot the resulting hull overlayed over the original grid. Default is `TRUE`.

Value

A data frame with two columns, x and y, containing the resampled coordinate grid. When hull is specified, any points not in the hull will be absent.

Examples

data("warps")

warps_fnc <- as_fnc_df(warps)

# hull with plot to see the hull
grid <- resample_grid(warps_fnc[c("x", "y")],
                      hull = "concaveman", plot = TRUE)
str(grid)

## Not run: 
# Alpha hull with plot to see the hull
grid <- resample_grid(warps_fnc[c("x", "y")],
                      hull = "alphahull", plot = TRUE)

## End(Not run)