Main Content

cdflib.createVar

Create new variable

Syntax

varnum = cdflib.createVar(cdfId, varname, datatype, numElements, dims, recVariance, dimVariance)

Description

varnum = cdflib.createVar(cdfId, varname, datatype, numElements, dims, recVariance, dimVariance) creates a new variable in the Common Data Format (CDF) file with the specified characteristics.

Input Arguments

cdfId

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

varname

Character vector or string scalar that specifies the name you want to assign to the variable.

datatype

Data type of the variable, specified as one of the following character vectors or string scalars containing a valid CDF data type, or its numeric equivalent.

CDF Data TypeDescription
'CDF_BYTE1-byte, signed integer
'CDF_CHAR'

1 byte, signed character data type that maps to the MATLAB® char or string class

'CDF_INT1'1-byte, signed integer
'CDF_UCHAR'

1 byte, unsigned character data type that maps to the MATLAB uint8 class

'CDF_UINT1'1-byte, unsigned integer
'CDF_INT2'2-byte, signed integer
'CDF_UINT2'2-byte, unsigned integer
'CDF_INT4'4-byte, signed integer
'CDF_UINT4'4-byte, unsigned integer
'CDF_FLOAT'4-byte, floating point
'CDF_REAL4'4-byte, floating point
'CDF_REAL8'8-byte, floating point.
'CDF_DOUBLE'8-byte, floating point
'CDF_EPOCH'8-byte, floating point
'CDF_EPOCH16'two 8-byte, floating point

numElements

Number of elements per datum. Value should be 1 for all data types, except for 'CDF_CHAR' and 'CDF_UCHAR'.

dims

A vector of the dimensions extents; empty if there are no dimension extents.

recVariance

Specifies record variance: true or false.

dimVariance

A vector of logicals; empty if there are no dimensions.

Output Arguments

varNum

The numeric identifier for the variable. Variable numbers are zero-based.

Examples

Create a CDF file and then create a variable named 'Time' in the CDF. The variable has no dimensions and varies across records. To run this example, you must be in a writable folder.

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

% Initially the file contains no variables
info = cdflib.inquire(cdfId)
info = 

  struct with fields:

     encoding: 'IBMPC_ENCODING'
     majority: 'ROW_MAJOR'
       maxRec: -1
      numVars: 0
    numvAttrs: 0
    numgAttrs: 0
% Create a variable in the file
varNum = cdflib.createVar(cdfId,"Time","cdf_int1",1,[],true,[]);

% Retrieve info about the file again to verify variable was created
% Note value of numVars field is now 1
info = cdflib.inquire(cdfId)
info = 

  struct with fields:

     encoding: 'IBMPC_ENCODING'
     majority: 'ROW_MAJOR'
       maxRec: -1
      numVars: 1
    numvAttrs: 0
    numgAttrs: 0
% Clean up
cdflib.delete(cdfId)
clear cdfId

Tips

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

  • 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

|

Topics