Grid interpolation.
The function interpolates the data of infile1 to the grid of infile2. From
infile2 only the grid information is used.
By default, a nearest neighbor interpolation provided by
get.knnx is used. For interpolation between
regular grids a simple bilinear interpolation as provided by
interp.surface.grid as well as a conservative
remapping as provided by remapcon can be chosen.
remap( var, infile1, infile2, outfile, method = "nearest", nc34 = 4, overwrite = FALSE, verbose = FALSE )
var |
Name of NetCDF variable (character). |
infile1 |
Filename of first input NetCDF file. This may include the directory (character). The data of infile1 are interpolated. |
infile2 |
Filename of second input file. This may include the directory (character). The grid information of infile2 are the target grid for the interpolation. This File may also be an ASCII-File containing the grid information. |
outfile |
Filename of output NetCDF file. This may include the directory (character). |
method |
Method used for remapping (character). Options are "bilinear" for bilinear interpolation, "conservative" for conservative remapping (only for regular grids, respectively) and "nearest" for nearest-neighbor interpolation. Default is "nearest". |
nc34 |
NetCDF version of output file. If |
overwrite |
logical; should existing output file be overwritten? |
verbose |
logical; if TRUE, progress messages are shown |
A NetCDF file including the interpolated data of infile1 on the grid of infile2 is written.
Other data manipulation functions:
acsaf_box_mergetime(),
add_grid_info(),
box_mergetime(),
cmsaf.transform.coordinate.system(),
levbox_mergetime()
## Create an example NetCDF file with a similar structure as used by CM
## SAF. The file is created with the ncdf4 package. Alternatively
## example data can be freely downloaded here: <https://wui.cmsaf.eu/>
library(ncdf4)
## create some (non-realistic) example data
lon <- seq(5, 15, 0.5)
lat <- seq(45, 55, 0.5)
lon2 <- seq(5, 15, 1)
lat2 <- seq(45, 55, 1)
time <- c(as.Date("2000-01-01"), as.Date("2001-02-01"))
origin <- as.Date("1983-01-01 00:00:00")
time <- as.numeric(difftime(time, origin, units = "hour"))
data1 <- array(250:350, dim = c(21, 21, 1))
data2 <- array(230:320, dim = c(21, 21, 1))
## create two example NetCDF files
x <- ncdim_def(name = "lon", units = "degrees_east", vals = lon)
y <- ncdim_def(name = "lat", units = "degrees_north", vals = lat)
t <- ncdim_def(name = "time", units = "hours since 1983-01-01 00:00:00",
vals = time[1], unlim = TRUE)
var1 <- ncvar_def("SIS", "W m-2", list(x, y, t), -1, prec = "short")
vars <- list(var1)
ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file_1.nc"), vars)
ncvar_put(ncnew, var1, data1)
ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew)
x <- ncdim_def(name = "lon", units = "degrees_east", vals = lon2)
y <- ncdim_def(name = "lat", units = "degrees_north", vals = lat2)
t <- ncdim_def(name = "time", units = "hours since 1983-01-01 00:00:00",
vals = time[1], unlim = TRUE)
ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file_2.nc"), vars)
ncvar_put(ncnew, var1, data2)
ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew)
## Interpolate the fields of both example CM SAF NetCDF file 1 to the
## coarser grid of file 2 and write the result into one output file.
remap(var = "SIS", infile1 = file.path(tempdir(),"CMSAF_example_file_1.nc"),
infile2 = file.path(tempdir(),"CMSAF_example_file_2.nc"),
outfile = file.path(tempdir(),"CMSAF_example_file_remap.nc"))
unlink(c(file.path(tempdir(),"CMSAF_example_file_1.nc"),
file.path(tempdir(),"CMSAF_example_file_2.nc"),
file.path(tempdir(),"CMSAF_example_file_remap.nc")))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.