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Read time variable in a netCDF File

Source: R/tnet_nc_read_time.R
nc_read_time.Rd

Will read the "time" variable in a netcdf file, and transform in a POSIXc vector using the units attribute of the time variable.

Usage

nc_read_time(nc_file)

Arguments

netcdf_file

object created by ncdf4::nc_open()

Value

vector with all dates in POSIXc format

Details

The units attribute must be in the following format: ":TIME: since :DATE:".
:TIME: can have the following values:

  • days -> :DATE: format by default is %Y-%m-%d

  • hours -> :DATE: format by default is %Y-%m-%d %H:%M:%S

  • seconds -> :DATE: format by default is %Y-%m-%d %H:%M:%S

If the attribute "date_format" exist, it will be use for :DATE: format.

See also

ncdf4::nc_open()

Examples


#Exemple with no "date_format" attributes
file <- "path\to\netCDFfile"
nc_file <- nc_open(file)
#> Error in R_nc4_open: No such file or directory
#> Error in nc_open(file): Error in nc_open trying to open file path	o
#> etCDFfile (return_on_error= FALSE )

nc_file
#> Error: object 'nc_file' not found
#>      1 variables (excluding dimension variables):
#>        double Bm[time,gid]   (Chunking: [4018,100])  
#>        units: m
#>        
#>      2 dimensions:
#>        time  Size:4018 
#>          units: days since 2010-08-01
#>          long_name: time
#>        gid  Size:33612 
#>          units: Segments_ID
#>          long_name: gid

time <- nc_read_time(nc_file)
#> Error: object 'nc_file' not found
time
#> function (x, ...) 
#> UseMethod("time")
#> <bytecode: 0x556f4d3a9000>
#> <environment: namespace:stats>
#>    [1] "2010-08-01 GMT" "2010-08-02 GMT" "2010-08-03 GMT" "2010-08-04 GMT"
#>    [5] "2010-08-05 GMT" "2010-08-06 GMT" "2010-08-07 GMT" "2010-08-08 GMT"
#>    [9] "2010-08-09 GMT" "2010-08-10 GMT" "2010-08-11 GMT" "2010-08-12 GMT"
#>    ...


#Exemple with "date_format" attributes
file <- "path\to\netCDFfile"
nc_file <- nc_open(file)
#> Error in R_nc4_open: No such file or directory
#> Error in nc_open(file): Error in nc_open trying to open file path	o
#> etCDFfile (return_on_error= FALSE )

nc_file
#> Error: object 'nc_file' not found
#>      1 variables (excluding dimension variables):
#>        float data[time,gid]   (Contiguous storage)  
#>        variable_name: Tw_NFS
#>          units: celsius_degrees
#>          long_name: water temperature at the final node
#>      
#>      2 dimensions:
#>        gid  Size:1 
#>          units: segments_IDs
#>        time  Size:96432 
#>          units: hours since 01/08/2010 00:00:00
#>          date_format: %d/%m/%Y %H:%M:%S
       
       
time <- nc_read_time(nc_file)
#> Error: object 'nc_file' not found

time
#> function (x, ...) 
#> UseMethod("time")
#> <bytecode: 0x556f4d3a9000>
#> <environment: namespace:stats>
#>    [1] "2010-08-01 00:00:00 GMT" "2010-08-01 01:00:00 GMT"
#>    [3] "2010-08-01 02:00:00 GMT" "2010-08-01 03:00:00 GMT"
#>    [5] "2010-08-01 04:00:00 GMT" "2010-08-01 05:00:00 GMT"
#>    ...