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cdflib.setVarCompression

Specify compression settings used with variable

Syntax

cdflib.setVarCompression(cdfId,varNum,ctype,cparams)

Description

cdflib.setVarCompression(cdfId,varNum,ctype,cparams) configures the compression setting for a variable in a Common Data Format (CDF) file.

Input Arguments

cdfId

Identifier of a CDF file, returned by a call to cdflib.create or cdflib.open.

varNum

Numeric value identifying a variable in the file. Variable identifiers (variable numbers) are zero-based.

ctype

One of the following character vectors or string scalars specifying the compression type, or its numeric equivalent.

ValueCompression Type
'NO_COMPRESSION'No compression.
'RLE_COMPRESSION'Run-length encoding compression
'HUFF_COMPRESSION'Huffman compression
'AHUFF_COMPRESSION'Adaptive Huffman compression
'GZIP_COMPRESSION'GNU's zip compression

To get the numeric equivalent of these compression type values, use cdflib.getConstantValue.

cparams

Optional parameter specifying any additional parameters required by the compression type. Currently, the only compression type that uses this parameter is 'GZIP_COMPRESSION'. For this compression type, you use cparms to specify the level of compression as a numeric value between 1 and 9.

Examples

Create a CDF, create a variable, and then set the compression used by the variable. To run this example, you must be in a folder with execute permission.

cdfId = cdflib.create("your_file.cdf");

% Create a variable in the file
varNum = cdflib.createVar(cdfId,"Time","cdf_int1",1,[],true,[]);

% Check the compression setting of the variable
[ctype,params,percent] = cdflib.getVarCompression(cdfId,0)
ctype =

    'NO_COMPRESSION'


params =

     []


percent =

   100
% Specify the compression used by the variable
cdflib.setVarCompression(cdfId,0,"GZIP_COMPRESSION",8)

% Check the new compression setting of the variable
[ctype,params,percent] = cdflib.getVarCompression(cdfId,0)
ctype =

    'GZIP_COMPRESSION'


params =

     8


percent =

     0
%Clean up
cdflib.delete(cdfId)
clear cdfId

Tips

  • This function corresponds to the CDF library C API routine CDFsetzVarCompression.

  • To use this function, you must be familiar with the CDF C interface. You can access the CDF documentation at the CDF website.

See Also

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