Determine monthly means
The function determines monthly mean values from data of a single CM SAF NetCDF input file. This function is applicable to 3-dimensional NetCDF data. There is a difference between the operators monmean and monavg. The mean is regarded as a statistical function, whereas the average is found simply by adding the sample members and dividing the result by the sample size. For example, the mean of 1, 2, miss and 3 is (1 + 2 + 3)/3 = 2, whereas the average is (1 + 2 + miss + 3)/4 = miss/4 = miss. If there are no missing values in the sample, the average and mean are identical.
monmean(var, infile, outfile, nc34 = 4, overwrite = FALSE, verbose = FALSE)
var |
Name of NetCDF variable (character). |
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 |
overwrite |
logical; should existing output file be overwritten? |
verbose |
logical; if TRUE, progress messages are shown |
A NetCDF file including a time series of monthly means is written.
Other monthly statistics:
mon.anomaly(),
monavg(),
mondaymean(),
monmax(),
monmin(),
monpctl(),
monsd(),
monsum(),
monvar(),
multimonmean(),
multimonsum(),
ymonmax(),
ymonmean(),
ymonmin(),
ymonsd(),
ymonsum()
## 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("2000-03-31"), "days")
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, 91))
## 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)
## Determine the monthly mean of the example CM SAF NetCDF file and
## write the output to a new file.
monmean(var = "SIS", infile = file.path(tempdir(),"CMSAF_example_file.nc"),
outfile = file.path(tempdir(),"CMSAF_example_file_monmean.nc"))
unlink(c(file.path(tempdir(),"CMSAF_example_file.nc"),
file.path(tempdir(),"CMSAF_example_file_monmean.nc")))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.