GetNetCDFAtCoords: Extract nearest neighbour timeseries

In EarthSystemDiagnostics/ncdftools: An R package of tools to handle NetCDF files

Description

Extract from a netcdf file the timeseries from the grid cells which are nearest to a set of requested coordinates. This function is useful if you want to analyse only a relatively small number of grid cells from a netcdf file and you do not necessarily need the entire spatial field.

Usage

GetNetCDFAtCoords(
  filename,
  req.coords,
  req.var,
  time.var = "time",
  lon.var = "longitude",
  lat.var = "latitude",
  verbose = FALSE
)

Arguments

filename	path to the netcdf file.
req.coords	matrix or dataframe of requested longitude (1st column) and latitude (2nd column) coordinates.
req.var	name of the timeseries variable to extract from the netcdf file.
time.var	name of the time variable in the netcdf file.
lon.var	name of the longitude variable in the netcdf file.
lat.var	name of the latitude variable in the netcdf file.
verbose	logical; if TRUE processing and run time information are printed to the terminal.

Value

A data frame of n rows, where n is the product of the number of requested coordinates and the time steps in the netcdf file, and five columns with the requested longitude, requested latitude, index number of the requested coordinate as character vector, time step, and timeseries value for the requested variable at each time step.

Author(s)

Andrew Dolman with contributions from Thomas Muench

Examples

filename <- system.file("extdata", "test_data.nc", package = "ncdftools")
req.coords = data.frame(lon = c(18, 13), lat = c(59, 52))

GetNetCDFAtCoords(filename, req.coords = req.coords, req.var = "t2m")

## print information on the processing step
## Not run: 
GetNetCDFAtCoords(filename, req.coords = req.coords, req.var = "grid_index",
                  verbose = TRUE)

## End(Not run)

EarthSystemDiagnostics/ncdftools documentation built on March 11, 2021, 6:03 p.m.