netcdf.defVarDeflate

Define compression parameters for netCDF variable

Syntax

netcdf.defVarDeflate(ncid,varid,shuffle,deflate,deflateLevel)

Description

netcdf.defVarDeflate(ncid,varid,shuffle,deflate,deflateLevel) sets the compression parameters for the netCDF variable specified by varid, in the location specified by ncid.

Examples

Create and Set Compression Level for NetCDF Variable

This example creates a variable with dimensions [1800 3600] and a compression level of 5. The result is a chunked layout that is a 10-by-10 grid. Use the netcdf.defVarChunking function to define your own chunking, otherwise netcdf.defVarDeflate uses the default library values.

ncid = netcdf.create("myfile.nc","NETCDF4");
latdimid = netcdf.defDim(ncid,"lat",1800);
londimid = netcdf.defDim(ncid,"col",3600);
varid = netcdf.defVar(ncid,"earthgrid","double",[latdimid londimid]);
netcdf.defVarChunking(ncid,varid,"CHUNKED",[180 360]);
netcdf.defVarDeflate(ncid,varid,true,true,5);
netcdf.close(ncid);

Input Arguments

ncid — File identifier

nonnegative integer scalar

Identifier of a netCDF file, returned by netcdf.create or netcdf.open, or of a netCDF group, returned by netcdf.defGrp, specified as a nonnegative integer scalar.

Data Types: double

varid — NetCDF variable identifier

nonnegative integer scalar

NetCDF variable identifier, specified as a nonnegative integer scalar. A variable identifier is returned by the netcdf.defVar function.

Data Types: double

varid — Variable identifier

nonnegative integer scalar

Identifier of netCDF variable, returned by netcdf.defVar, specified as a nonnegative integer scalar.

Data Types: double

shuffle — Status of shuffle filter

false or 0 | true or 1

Status of the shuffle filter, specified as a numeric or logical 0 (false) or 1 (true). A value of false disables the shuffle filter, and true enables it. The shuffle filter assists with the compression of integer data by changing the byte order in the data stream. You cannot set shuffle to true if varid refers to a variable of type NC_STRING or NC_VLEN.

Data Types: logical

deflate — Status of deflate filter

false or 0 | true or 1

Status of the deflate filter, specified as a numeric or logical 0 (false) or 1 (true). Specify deflate as true to enable compression, and then specify deflateLevel as the intended positive compression level. Specify deflate as false to disable compression. The value of deflate is automatically set to false if deflateLevel is specified as 0.

Data Types: logical

deflateLevel — Level of compression

integer scalar value between 0 and 9

Level of compression, specified as an integer scalar value between 0 and 9. A value of 0 indicates no compression and is equivalent to specifying the value of deflate as false. A value of 1 indicates the least compression, and a value of 9 indicates the most. The value of deflateLevel is ignored if deflate is false.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Limitations

• You cannot set deflate to true and deflateLevel to a positive value if varid refers to a variable of type NC_STRING or NC_VLEN.

Tips

• This function corresponds to the nc_def_var_deflate function in the netCDF library C API.

Version History

Introduced in R2010b

R2023b: Setting deflateLevel to 0 disables the deflate filter

Setting the compression level to zero disables the deflate filter. Previously, the deflate filter could be enabled with a compression level of zero.

R2023b: Use compression and shuffle filter only with fixed-length data types

Compression and the shuffle filter can be used only with fixed-length data types and generate an error if applied to variables of type NC_STRING or NC_VLEN. Previously, if you specified compression or the shuffle filter for NC_STRING or NC_VLEN variables, the specification had no effect.