netcdf.getVar

Read data from NetCDF variable

Syntax

data = netcdf.getVar(ncid,varid) data = netcdf.getVar(ncid,varid,start) data = netcdf.getVar(ncid,varid,start,count) data = netcdf.getVar(ncid,varid,start,count,stride) data = netcdf.getVar(___,output_type)

Description

data = netcdf.getVar(ncid,varid) returns data, the value of the variable specified by varid. ncid is a NetCDF file identifier returned by netcdf.create or netcdf.open. The returned value data is of the MATLAB^® data type that best matches the NetCDF data type of the variable specified by varid. For more information about how MATLAB determines the best match, see More About.

Note

For variables of type NC_CHAR, the netcdf.getVar function supports reading only of data that contain only ASCII-encoded characters. NetCDF-4 files support writing UTF-8-encoded characters in variables of type NC_STRING.

data = netcdf.getVar(ncid,varid,start) returns a single value starting at the specified index, start.

data = netcdf.getVar(ncid,varid,start,count) returns a contiguous section of a variable. start specifies the starting point and count specifies the amount of data to return.

data = netcdf.getVar(ncid,varid,start,count,stride) returns a subset of a section of a variable. start specifies the starting point, count specifies the extent of the section, and stride specifies which values to return.

data = netcdf.getVar(___,output_type) specifies the data type of the return value data. Specify output_type as one of these values:

"double"
"single"
"int64"
"uint64"
"int32"
"uint32"
"int16"
"uint16"
"int8"
"uint8"
"char"

This function corresponds to several functions in the NetCDF library C API. To use this function, you should be familiar with the NetCDF programming paradigm.

Examples

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Read Value of Variable in NetCDF File

Open Live Script

Open the example file, example.nc.

ncid = netcdf.open('example.nc','NC_NOWRITE');

Get the name of the first variable in the file.

varname = netcdf.inqVar(ncid,0)

varname = 
'avagadros_number'

Get variable ID of the first variable, given its name.

varid = netcdf.inqVarID(ncid,varname)

varid = 0

Get the value of the variable. Use the variable ID as the second input to the netcdf.getVar function.

data = netcdf.getVar(ncid,varid)

data = 6.0221e+23

Display the data type of the output value.

whos data

  Name      Size            Bytes  Class     Attributes

  data      1x1                 8  double

Get the value of the avogadros_number variable again, specifying that the output data type should be single.

data = netcdf.getVar(ncid,varid,'single');

Display the data type of the output value.

whos data

  Name      Size            Bytes  Class     Attributes

  data      1x1                 4  single

Close the NetCDF file.

netcdf.close(ncid)

More About

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NetCDF to MATLAB Data Type Conversion

When the optional input output_type is not specified, netcdf.getVar automatically chooses the MATLAB data type that best matches the NetCDF data type according to this table.

NetCDF Data Type	MATLAB Data Type
`NC_DOUBLE`	`double`
`NC_FLOAT`	`single`
`NC_INT64` (NetCDF-4 files only)	`int64`
`NC_UINT64` (NetCDF-4 files only)	`uint64`
`NC_INT`	`int32`
`NC_UINT` (NetCDF-4 files only)	`uint32`
`NC_SHORT`	`int16`
`NC_USHORT` (NetCDF-4 files only)	`uint16`
`NC_BYTE`	`int8`
`NC_UBYTE` (NetCDF-4 files only)	`uint8`
`NC_CHAR`	`char`
`NC_STRING` (NetCDF-4 files only)	`string`
User-defined `NC_VLEN` types (NetCDF-4 files only)	`cell`