att.inq.nc {RNetCDF}

Inquire About a NetCDF Attribute

Description

Inquire about a NetCDF attribute.

Usage

att.inq.nc(ncfile, variable, attribute)

Arguments

ncfile

Object of class NetCDF which points to the NetCDF dataset (as returned from open.nc).

variable

Either the ID or the name of the attribute's variable or "NC_GLOBAL" for a global attribute.

attribute

Either the ID or the name of the attribute to be inquired.

Details

This function returns information about a NetCDF attribute. Information about an attribute include its ID, its name, its type, and its length. In general, attributes are accessed by name rather than by their ID number because the attribute number is more volatile than the name, since it can change when other attributes of the same variable are deleted.

Valid attribute ID numbers range from 0 to the number of attributes minus 1. The number of attributes of a file, group, or variable can be found using the relevant inquiry function (file.inq.nc, grp.inq.nc, or var.inq.nc).

Value

A list containing the following components:

id

Attribute ID.

name

Attribute name.

type

External NetCDF data type as one of the following labels: NC_BYTE, NC_UBYTE, NC_CHAR, NC_SHORT, NC_USHORT, NC_INT, NC_UINT, NC_INT64, NC_UINT64, NC_FLOAT, NC_DOUBLE, NC_STRING, or a user-defined type name.

length

Length of this attribute.

Author(s)

Pavel Michna, Milton Woods

References

https://www.unidata.ucar.edu/software/netcdf/

Examples

##  Create a new NetCDF dataset and define two dimensions
file1 <- tempfile("att.inq_", fileext=".nc")
nc <- create.nc(file1)

dim.def.nc(nc, "station", 5)
dim.def.nc(nc, "time", unlim=TRUE)

##  Create two variables, one as coordinate variable
var.def.nc(nc, "time", "NC_INT", "time")
var.def.nc(nc, "temperature", "NC_DOUBLE", c(0,1))

##  Put some attributes
att.put.nc(nc, "temperature", "_FillValue", "NC_DOUBLE", -99999.9)
att.put.nc(nc, "NC_GLOBAL", "title", "NC_CHAR", "Data from Foo")

##  Inquire about these attributes
att.inq.nc(nc, "temperature", "_FillValue")
att.inq.nc(nc, "NC_GLOBAL", "title")

close.nc(nc)
unlink(file1)