ncinfo

Return information about netCDF data source

Syntax

finfo = ncinfo(source)

vinfo = ncinfo(source,varname)

ginfo = ncinfo(source,groupname)

Description

finfo = ncinfo(source) returns information about the entire netCDF data source specified by source.

vinfo = ncinfo(source,varname) returns information about the variable varname in source.

ginfo = ncinfo(source,groupname) returns information about the group groupname in source.

Examples

Find Dimensions with Names Matching a Pattern

Get the file schema of the netCDF file example.nc.

finfo = ncinfo("example.nc")

finfo = 

  struct with fields:

      Filename: 'matlabroot\toolbox\matlab\demos\example.nc'
          Name: '/'
    Dimensions: [1×3 struct]
     Variables: [1×3 struct]
    Attributes: [1×1 struct]
        Groups: [1×2 struct]
        Format: 'netcdf4'
     Datatypes: []

Find dimensions with names that begin with x.

dimNames = {finfo.Dimensions.Name};
dimMatch = strncmpi(dimNames,"x",1);
disp(finfo.Dimensions(dimMatch))

         Name: 'x'
       Length: 50
    Unlimited: 0

Get Size and Dimensionality of Variable

Get the variable schema of the peaks variable in the netCDF file example.nc.

vinfo = ncinfo("example.nc","peaks")

vinfo = 

  struct with fields:

        Filename: 'matlabroot\toolbox\matlab\demos\example.nc'
            Name: 'peaks'
      Dimensions: [1×2 struct]
            Size: [50 50]
        Datatype: 'int16'
      Attributes: [1×1 struct]
       ChunkSize: []
       FillValue: -32767
    DeflateLevel: []
         Shuffle: 0
          Format: 'netcdf4'

Find the size of the peaks variable.

varSize = vinfo.Size

varSize =

    50    50

Determine whether the peaks variable has any unlimited dimensions.

hasUnlimDim = any([vinfo.Dimensions.Unlimited])

hasUnlimDim =

  logical

   0

Find Unlimited Dimensions in Group

Get the group schema of the /grid2 group in the netCDF file example.nc.

ginfo = ncinfo("example.nc","/grid2")

ginfo = 

  struct with fields:

      Filename: 'matlabroot\toolbox\matlab\demos\example.nc'
          Name: 'grid2'
    Dimensions: [1×3 struct]
     Variables: [1×1 struct]
    Attributes: [1×1 struct]
        Groups: []
        Format: 'netcdf4'

Find unlimited dimensions in the group.

unlimDims = [ginfo.Dimensions.Unlimited];
disp(ginfo.Dimensions(unlimDims))

         Name: 'time'
       Length: 0
    Unlimited: 1

Input Arguments

source — Name of netCDF data source

string scalar | character vector

Name of the netCDF data source, specified as a string scalar or character vector. The source argument can be one of these values:

• The path of a local netCDF source

• The OPeNDAP URL of a remote OPeNDAP netCDF data source

• The HTTP URL of a remote netCDF source, with #mode=bytes appended to the end of the URL to enable byte-range reading

  Note

  Byte-range reading is slower than other methods for reading from remote sources. For more details about byte-range reading, see the netCDF documentation.

Example: "myNetCDFfile.nc"

Example: "http://host_name/netcdf_filename#mode=bytes"

varname — Variable name

string scalar | character vector

Variable name, specified as a string scalar or character vector containing the name of a variable in the netCDF data source.

If source specifies a file with format netcdf4, you can specify the location of the variable within the group hierarchy by specifying varname as a fully qualified name.

Example: "myVar"

Example: "/myGrp/mySubGrp/myNestedVar"

groupname — Group name

string scalar | character vector

Group name, specified as a string scalar or character vector containing the name of a group in the netCDF data source.

Example: "myGrp"

Example: "/myGrp/mySubGrp"

Output Arguments

finfo — NetCDF file schema

structure

NetCDF file schema, returned as a structure. This table describes the fields of the structure.

Field	Description
Filename	NetCDF filename or OPeNDAP URL, returned as a character vector
Name	'/' (indicating the full file)
Dimensions	Dimension schema, returned as a structure vector containing these fields: Name — Name of the dimension, returned as a character vector Length — Length of the dimension, returned as a nonnegative integer (a value of 0 represents an unlimited dimension) Unlimited — Whether the dimension is unlimited, returned as a logical scalar
Variables	Variable schema, as described in the vinfo output argument, except without the Filename and Format fields
Attributes	Attribute schema, returned as a structure vector containing these fields: Name — Name of the attribute, returned as a character vector Value — Value of the attribute
Groups	Group schema, as described in the ginfo output argument, except without the Filename and Format fields, or an empty array ([]) if the file is not of format netcdf4
Format	NetCDF file format, returned as a character vector
Datatypes	Structure vector of user-defined data types, containing these fields (or an empty array ([]) if there are no user-defined data types): Name — Name of the data type, returned as a character vector Class — 'NC_VLEN' Type — MATLAB® type of the data type, returned as a character vector ByteSize — Size of the type in bytes, returned as a positive integer

vinfo — NetCDF variable schema

structure

NetCDF variable schema, returned as a structure. This table describes the fields of the structure.

Field	Description
Filename	NetCDF filename or OPeNDAP URL, returned as a character vector
Name	Name of the variable, returned as a character vector
Dimensions	Dimension schema for the variable, returned as a structure vector containing these fields: Name — Name of the dimension, returned as a character vector Length — Length of the dimension, returned as a nonnegative integer (a value of 0 represents an unlimited dimension) Unlimited — Whether the dimension is unlimited, returned as a logical scalar
Size	Size of the current variable, returned as a numeric scalar or vector
Datatype	MATLAB data type of the variable or name of the user-defined type, returned as a character vector
Attributes	Attribute schema for the variable, returned as a structure vector containing these fields: Name — Name of the attribute, returned as a character vector Value — Value of the attribute
ChunkSize	Chunk size for the variable, returned as a numeric value, if defined; otherwise, an empty array ([])
FillValue	Fill value for the variable, returned as a scalar, if defined; otherwise, an empty array ([])
DeflateLevel	Deflate compression level for the variable, returned as a nonnegative integer, if enabled; otherwise, an empty array ([])
Shuffle	Whether the shuffle filter is enabled for the variable, returned as a logical scalar
Format	NetCDF file format, returned as a character vector

ginfo — NetCDF group schema

structure

NetCDF group schema, returned as a structure. This table describes the fields of the structure.

Field	Description
Filename	NetCDF filename or OPeNDAP URL, returned as a character vector
Name	Name of the group, returned as a character vector
Dimensions	Dimension schema for the group, returned as a structure vector containing these fields: Name — Name of the dimension, returned as a character vector Length — Length of the dimension, returned as a nonnegative integer (a value of 0 represents an unlimited dimension) Unlimited — Whether the dimension is unlimited, returned as a logical scalar
Variables	Variable schema for the group, as described in the vinfo output argument, except without the Filename and Format fields
Attributes	Attribute schema for the group, returned as a structure vector containing these fields: Name — Name of the attribute, returned as a character vector Value — Value of the attribute
Groups	Group schema for the group, as described in this output argument, except without the Filename and Format fields
Format	NetCDF file format, returned as a character vector

Tips

• Use ncdisp for visual inspection of a netCDF source.

Version History

Introduced in R2011a

R2022a: Byte-range reading of remote datasets

You can use ncinfo for read-only access to remote datasets using the HTTP byte-range capability, provided that the remote server supports byte-range access.