resample_csquares {csquares}

Resample csquares to a different resolution

Description

Resample csquares objects to higher or lower resolutions.

Usage

resample_csquares(x, method = "target", ..., resolution, magnitude = 1L)

Arguments

x

A csquares object to be resampled to a different resolution

method

Method for determining the resolution of the resulting csquares. Should be one of "target", "min", "max", "up", or "down". "target" will resample x to the level specified with resolution

...

When x inherits the stars class and the resulting object has a lower resolution than x, the dots are passed on to dplyr::summarise(). This allows you to summarise columns to the lower resolution.

resolution

Resolution (in WGS84 degrees) to be used for creating c-squares codes. As per c-square specifications, the resolution should be 10 or less, yet greater than 0. It should be a tenfold of 1 or 5. Valid resolutions are therefore: 10, 5, 1, 0.5, 0.1, etc.

magnitude

When method == "up" or "down", this parameter specifies the number of steps to increase or decrease the resolution. Should be a positive integer.

Value

A csquares object based on x

Author(s)

Pepijn de Vries

Examples

csq    <- as_csquares(c("1000", "5000:2|5000:100", "3000:100:100"))
csq_df <- as_csquares(data.frame(csq = csq, foobar = letters[1:3]), csquares = "csq")

## Resample csquares based on the one with the lowest resolution:
resample_csquares(csq,    "min")

## Resample csquares to a specific resolution
resample_csquares(csq,    "target", resolution = 5)

## Same, but applied to a csquares object inheriting from a data.frame
resample_csquares(csq_df, "target", resolution = 5)

## Same, but applied to a csquares object inheriting the `sf` class
## Note that the geometry is updated based on the resampled csquares
if (requireNamespace("sf")) {
  library(sf)
  csq_sf <- st_as_sf(csq_df)
  resample_csquares(csq_sf, "target", resolution = 5)
}

## Resample csquares one step down.
resample_csquares(csq,    "down")
resample_csquares(csq_df, "down")

if (requireNamespace(c("dplyr", "stars"))) {
  ## Csquares objects can inherit from the stars class as well.
  ## These too can be resampled. But additional columns need
  ## to be summarised when the resulting resolution is lower
  ## than the original:
  g <-
    sf::st_bbox(c(xmin = 4.0, xmax = 6.5, ymin = 52.5, ymax = 53), crs = 4326) |>
      new_csquares(resolution = 0.1) |>
      ## add a column with some random positive numbers:
      dplyr::mutate(random = .data$csquares |> length() |> rnorm() |> exp())

  ## Resample stars object to lower resolution
  g_sum <- resample_csquares(g, resolution = 10, random = sum(random, na.rm = TRUE))

  ## And back to a higher resolution (note that you have lost information as it was summarised
  ## in the previous step)
  resample_csquares(g_sum, "up", random = sum(random, na.rm = TRUE))
}