ncwriteschema

R2026b

Add netCDF schema definitions to netCDF file

Syntax

ncwriteschema(filename,schema)

Description

ncwriteschema(filename,schema) creates or adds attributes, dimensions, variable definitions, and group structure defined in schema to the netCDF file filename.

You can use the ncwriteschema function in combination with the ncinfo function to create a netCDF file based on the schema of an existing file.

• The ncwriteschema function does not write variable data. Use the ncwrite function to write data to the created variables. Unlimited dimensions have an initial size of 0 until you write data.

• The ncwriteschema function cannot change the format of an existing file. It cannot redefine existing variables or dimensions in filename. If schema contains attributes, dimensions, variable definitions, or a group structure that already exist in the file, then the ncwriteschema function issues a warning but continues processing.

• The ncwriteschema function cannot create new files in the 64-bit data format. To create a file in this format, use the netcdf.create function with the '64BIT_DATA' creation mode.

Examples

Create File Using Dimension Definitions

Define the schema for a classic format netCDF file with two dimension definitions. Then write the schema to a netCDF file.

mySchema.Name = "/";
mySchema.Format = "classic";
mySchema.Dimensions(1).Name = "time";
mySchema.Dimensions(1).Length = Inf;
mySchema.Dimensions(2).Name = "rows";
mySchema.Dimensions(2).Length = 10;
ncwriteschema("emptyFile.nc",mySchema)

Display the contents of emptyfile.nc.

ncdisp("emptyfile.nc")

Source:
           pwd\emptyfile.nc
Format:
           classic
Dimensions:
           time = 0     (UNLIMITED)
           rows = 10

Create File Using Existing Variable Schema

Use the ncinfo function to get the schema of the peaks variable from the file example.nc, and write this schema to a new file.

myVarSchema = ncinfo("example.nc","peaks");
ncwriteschema("peaksFile.nc",myVarSchema)

Read the data for peaks from example.nc, write it to the new file, and verify the results.

peaksData = ncread("example.nc","peaks");
ncwrite("peaksFile.nc","peaks",peaksData)
ncdisp("peaksFile.nc")

Source:
           pwd\peaksFile.nc
Format:
           netcdf4
Dimensions:
           x = 50
           y = 50
Variables:
    peaks
           Size:       50x50
           Dimensions: x,y
           Datatype:   int16
           Attributes:
                       _FillValue  = -32767
                       description = 'z = peaks(50);'

Input Arguments

filename — Filename

string scalar | character vector

Filename, specified as a string scalar or character vector. Specify the name of an existing netCDF file or the name you want to assign to a new netCDF file.

If filename does not exist, then the ncwriteschema function creates the netCDF file using the netcdf4_classic format, unless the Format field in schema specifies another format.

Example: "myFile.nc"

schema — NetCDF file, group, dimension, or variable schema

structure | structure array

NetCDF file, group, dimension, or variable schema, specified as a structure or structure array. The schema argument can represent either a netCDF file, one or more groups in a netCDF file of format netcdf4, one or more netCDF dimensions, or one or more netCDF variables. A file or group schema can contain a field for a variable schema, a field for a dimension schema, or both. You can use the output of the ncinfo function as a schema.

This table lists the fields in the different types of schemas. In this table:

• Optional fields are marked with an asterisk (*).

• Fields and schema types that apply only to data with format netcdf4 are marked with a dagger (†).

• Fields that apply only to data with format netcdf4 or netcdf4_classic are marked with a pound sign (#).

Schema Type	Field	Description
File schema	Name	"/"
	Groups (†) (*)	Group schema, specified as a structure or structure array
	Dimensions (*)	Dimension schema, specified as a structure or structure array
	Variables (*)	Variable schema, specified as a structure or structure array
	Attributes (*)	Attribute schema, specified as a structure array containing Name (string scalar or character vector) and Value fields
	Format (*)	NetCDF file format, specified as "classic", "64bit", "netcdf4_classic", or "netcdf4"
Group schema (†)	Name	Group name, specified as a string scalar or character vector
	Groups (*)	Group schema, specified as a structure or structure array
	Dimensions (*)	Dimension schema, specified as a structure or structure array
	Variables (*)	Variable schema, specified as a structure or structure array
	Attributes (*)	Attribute schema, specified as a structure array containing Name (string scalar or character vector) and Value fields
	Format (*)	NetCDF file format, specified as "classic", "64bit", "netcdf4_classic", or "netcdf4" Note The ncwriteschema function ignores this field if the group schema is inside a file or group schema.
Dimension schema	Name	Dimension name, specified as a string scalar or character vector
	Length	Dimension length, specified as a nonnegative integer (can be Inf or 0 for unlimited dimensions)
	Unlimited (*)	Whether the dimension is unlimited, specified as a logical scalar Note If the value of this field is true, then the ncwriteschema function sets the Length field to 0.
	Format (*)	NetCDF file format, specified as "classic", "64bit", "netcdf4_classic", or "netcdf4" Note The ncwriteschema function ignores this field if the dimension schema is inside a file or group schema.
Variable schema	Name	Variable name, specified as a string scalar or character vector
	Dimensions	Dimension schema, specified as a structure or structure array
	Datatype	MATLAB® data type, specified as a string scalar or character vector
	Attributes (*)	Attribute schema, specified as a structure array containing Name (string scalar or character vector) and Value fields
	ChunkSize (*) (†)	Chunk size for the variable, specified as a numeric scalar
	FillValue (*) (#)	Fill value of the variable, specified as a numeric scalar or text
	DeflateValue (*) (†)	Deflate compression level of the variable, specified as a nonnegative integer
	Shuffle (*) (†)	Whether the shuffle filter is enabled, specified as a logical scalar
	Format (*)	NetCDF file format, specified as "classic", "64bit", "netcdf4_classic", or "netcdf4" Note The ncwriteschema function ignores this field if the variable schema is inside a file or group schema.

Data Types: struct

Version History

Introduced in R2011a