cmsaf.mulc: Multiply data with a constant.

In cmsafops: Tools for CM SAF NetCDF Data

Multiply data with a constant.

Description

This function multiplies each element of a dataset with a given constant number.

Usage

cmsaf.mulc(
  var,
  const = 1,
  infile,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE,
  nc = NULL
)

Arguments

var	Name of NetCDF variable (character).
const	Constant number (numeric).
infile	Filename of input NetCDF file. This may include the directory (character).
outfile	Filename of output NetCDF file. This may include the directory (character).
nc34	NetCDF version of output file. If nc34 = 3 the output file will be in NetCDFv3 format (numeric). Default output is NetCDFv4.
overwrite	logical; should existing output file be overwritten?
verbose	logical; if TRUE, progress messages are shown
nc	Alternatively to infile you can specify the input as an object of class ncdf4 (as returned from ncdf4::nc_open).

Value

A NetCDF file including the manipulated data fields of infile is written. Standard output precision is 'double'.

See Also

Other mathematical operators: cmsaf.abs(), cmsaf.addc(), cmsaf.add(), cmsaf.divc(), cmsaf.div(), cmsaf.mul(), cmsaf.subc(), cmsaf.sub(), divdpm(), muldpm()

Examples

## 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)
time <- seq(as.Date("2000-01-01"), as.Date("2010-12-31"), "month")
origin <- as.Date("1983-01-01 00:00:00")
time <- as.numeric(difftime(time, origin, units = "hour"))
data <- array(250:350, dim = c(21, 21, 132))

## create example NetCDF

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, 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.nc"), vars)
ncvar_put(ncnew, var1, data)
ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew)

## Multiply each dataset element of the example CM SAF NetCDF file by a
## given number and write the output to a new file.
cmsaf.mulc(var = "SIS", const = 10, infile = file.path(tempdir(),
 "CMSAF_example_file.nc"), outfile = file.path(tempdir(),
 "CMSAF_example_file_mulc.nc"))

unlink(c(file.path(tempdir(),"CMSAF_example_file.nc"), 
 file.path(tempdir(),"CMSAF_example_file_mulc.nc")))

cmsafops documentation built on Sept. 18, 2023, 5:16 p.m.