SelPoint: Select nearest point
In EarthSystemDiagnostics/pfields: An R Package to Analyse Gridded Field Data

Description Usage Arguments Details Value Author(s) Examples

Select the timeseries from a "pField" object at the grid point nearest to a given pair of latitude and longitude values.

1	SelPoint(data, lat, lon, simplify = TRUE, verbose = FALSE)

`data`	a `"pField"` object.
`lat`	the latitude of the requested point.
`lon`	the longitude of the requested point.
`simplify`	logical; if `TRUE` (the default) the result will be simplified to a `"pTs"` object, otherwise it will be a `"pField"` object with only one spatial dimension.
`verbose`	if `TRUE`, print a message with the requested and nearest found coordinates. Defaults to `FALSE`.

This is a function in development; the current method to find the nearest grid point is to minimise the root mean square deviation between the position vectors in spherical coordinates of the requested point and all observation points in the "pField" object, which is done by calling MinimizeSpherical. In the future, a different method may be implemented for this. Note that requested lat/lon values outside the range of grid points in data will be processed with a warning.

a "pTs" or "pField" (if simplify = FALSE) object with the time series at the grid point nearest to the requested point.

Thomas Münch

# Create some empty pField object
lat <- seq(-75, -80, -5)
lon <- c(0, 135, 215)
time <- 1 : 4

x <- pField(lat = lat, lon = lon, time = time)

# Extract grid point nearest to lat = -80, lon = 200:
SelPoint(x, lat = -80, lon = 200, verbose = TRUE)
SelPoint(x, lat = -80, lon = 200, simplify = FALSE, verbose = TRUE)