Ref_man.rd

# RubyNetCDF Reference Manual

- Method Index

---------------------------------------------

## Overview

RubyNetCDF is the Ruby interface of the NetCDF library. Ruby is a free object-oriented scripting language and is freely available from the Ruby homepage. To handle numeric data, RubyNetCDF uses NArray, which is the standard numeric multi-dimensional array class for Ruby. Thus, you have to have installed it before installing this library. An NArray object holds numeric data in a consecutive memory area pointed by a C pointer. Thus, it is computationally efficient. NArray is similar to NumPy for Python, but results of some benchmark tests suggests that NArray is more efficient than NumPy. Optionally, RubyNetCDF offers methods to handle data missing automatically. To use it, you will also need NArrayMiss. See Usage for details.

### Structure

RubyNetCDF consists of the four classes in the following.

- class NetCDF -- the file class

  An NetCDF object represents a NetCDF file

- class NetCDFDim -- the dimension class

  Although in its C version a NetCDF dimension is represented by a combination of a file ID and a dimension ID, it is represented by only one NetCDFDim object in RubyNetCDF.

- class NetCDFVar -- the variable class

  Although in its C version a NetCDF variable is represented by a combination of a file ID and a variable ID, it is represented by only one NetCDFVar object in RubyNetCDF.

- class NetCDFAtt -- the attribute class

  Although in its C version a NetCDF attribute is represented by a combination of file ID, variable ID, and its name, it is represented by only one NetCDFAtt object in RubyNetCDF.

### Data type

All the NetCDF variable types char, byte, short, int, float, and double are supported in this Ruby interface. These types are called, however, differently in it to adhere to the convention of Ruby, or, more specifically, of NArray. These types are named to as "char", "byte", "sint", "int", "sfloat", and "float", respectively. Therefore, the vartype (=ntype) method of the NetCDFVar class returns one of these strings. The def_var method of the NetCDF class also accepts one of them to define a variable. It should be noted especially that "float" in this library means the double in the NetCDF terminology. This is due to the convention of Ruby -- the predefined Float class corresponds to the double in C, not the float.

The "get" method of NetCDFVar class reads a variable in a NArray of the same type as in the file, except for the "char" type which is read into a "byte". This is because NArray does not have a "char" type. However, it not is not supposed to be a problem, since a byte NArray can easily handle string data.

### Error handling

Errors are basically handled by raising exceptions. However, light errors in value-returning methods are handled by returning nil (e.g., if a non-existent attribute name is specified in attribute reading). Those methods that return nil on error are explicitly written as such in the following.

### Security features

Security handling is done just as in the pre-defined File class.

### Usage

To use the RubyNetCDF library, load the library first by placing the following line in your Ruby program to load the library:

    require 'numru/netcdf'

If you want to use automatic data-missing-handling methods (of NetCDFVar class), use the following:

    require 'numru/netcdf_miss'

This will call `require 'numru/netcdf'` inside at the beginning, so you do not have to call the both. The missing-data handling is done with NArrayMiss, so you have have installed it. This is, however, not needed if you only call `require 'numru/netcdf'`.

Here, 'numru', which stands for "Numerical Ruby", is the name of the subdirectory in the user's load path where the RubyNetCDF library is placed. Then, it can be used as in the following:

    file = NumRu::NetCDF.create('tmp.nc')
    x = file.def_dim('x',10)
    y = file.def_dim('y',10)
    v = file.def_var('v','float',[x,y])
    file.close

Here, NumRu is the module that has the library in it. The reason why NetCDF library is wrapped in such a module is to avoid conflicts in the name space. Without this kind of treatment, problems happen if the user wants to use a library that happens to have a class or module with the same name as even one of the classes in this library.

If such a problem is not expected to happen, the prefix "NumRu::" can be eliminated by "including" the NumRu module as in the following, so that to place "NumRu::" is not needed anymore in the current scope:

    include NumRu
    file = NetCDF.create('tmp.nc')
    ...

For more examples, see demo and test programs included in the distribution package.

---------------------------------------------

## How to read this manual

#### `method_name(argument1, argument2, ...) -- arguments that can be omitted are expressed as Argument_name=Default_value`

  Explanation of its function

  Arguments

  - name of argument1 (its class or possible values): explanation
  - name of argument2 (its class or possible values): explanation
  - ...

  Return value

  - Explanation of the return value

  Corresponding (dependent) function(s) in the C library of NetCDF

  - Name(s) in NetCDF ver 3. The function equivalent to the current method, if not in parenthesis. If no direct correspondence, dependent functions are listed in parentheses.

---------------------------------------------

## Method Index

- class NetCDF

  Class Methods

  - NetCDF.open Opens a file (class method). If mode="w" and non-existent, a new
  - NetCDF.new Aliased to NetCDF.open
  - NetCDF.create Creates a NetCDF file (class method)
  - NetCDF.create_tmp Creates a temporary NetCDF file (class method)

  Instance Methods

  - close Closes the file.
  - ndims Returns the number of dimensions in the file
  - nvars Returns the number of variables in the file
  - natts Returns the number of global attributes in the file
  - unlimited Returns the unlimited dimension in the file
  - path Returns the path of the file (contents of the filename specified when opened/created)
  - redef Switches to the define mode. Does nothing if already in it (nil returned).
  - enddef Switches to the data mode. Does nothing if already in it (nil returned).
  - define_mode? Inquire whether the file is in the define mode.
  - sync Synchronizes the disk copy of a netCDF dataset with in-memory buffer
  - def_dim Define a dimension
  - put_att Sets a global attribute
  - def_var Defines a variable
  - def_var_with_dim Same as def_var but defines dimensions first if needed
  - var Opens an existing variable in the file
  - vars Opens existing variables in the file
  - dim Opens an existing dimension in the file
  - dims Opens existing dimensions in the file
  - att Opens an existing global attribute in the file
  - fill= Sets a fill mode. (Default behavior of NetCDF is FILL.)
  - each_dim Iterator regarding the dimensions in the file.
  - each_var Iterator regarding the variables in the file.
  - each_att Iterator regarding the global attributes of the file.
  - dim_names Returns the names of all dimensions in the file
  - var_names Returns the names of all variables in the file
  - att_names Returns the names of all the global attributes of the file

- class NetCDFDim

  Class Methods

  Instance Methods

  - length Returns the length of the dimension
  - length_ul0 Same as length but returns 0 for the unlimited dimension
  - name= Rename the dimension
  - name Returns the name of the dimension
  - unlimited? Inquires whether the dimension is unlimited or not

- class NetCDFVar

  Class Methods

  - NetCDFVar.new Combines NetCDF.open and NetCDF#Var to open a variable with one line (no need to use this).
  - NetCDFVar.unpack_type= Fix the NArray type to be used in unpack
  - NetCDFVar.unpack_type Returns the NArray type set by NetCDFVar.unpack_type=.

  Instance Methods

  - dim Inquires the dim_num-th dimension of the variable (dim_num=0,1,2,..)
  - dims Returns an array of all the dimensions of the variable
  - shape_ul0 Returns the shape of the variable, but the length of the unlimited dimension is set to zero.
  - shape_current Returns the current shape of the variable.
  - each_att Iterator regarding the global attributes of the variables.
  - dim_names Returns the names of all the dimensions of the variable
  - att_names Returns the names of all the attributes of the variable
  - name Returns the name of the variable
  - name= Rename the variable
  - ndims Number of dimensions of the variable (which is rank of the variable).
  - rank aliased to ndims
  - ntype Aliased to vartype
  - vartype Inquires the data value type of the variable
  - typecode Inquires the data type of the variable (returns a typecode of NArray)
  - natts Returns the number of the attributes of the variable
  - file Inquires the file that the variable is in
  - att Returns the attribute specified by its name
  - put_att Sets an attribute
  - put Aliased to simple_put
  - simple_put Set the values of the variable
  - pack Pack a NArray (etc) using the attributes scale_factor and/or add_offset of self.
  - scaled_put Same as simple_put but interprets the attributes scale_factor and/or add_offset using pack.
  - get Aliased to simple_get
  - simple_get Returns values of the variable
  - unpack Unpack a NArray (etc) using the attributes scale_factor and/or add_offset of self.
  - scaled_get Same as simple_get but interprets the attributes scale_factor and/or add_offset using unpack.
  - [] Same as NetCDFVar#get but a subset is specified as in the method [] of NArray.
  - []= Same as NetCDFVar#put but a subset is specified as in the method []= of NArray.

  Instance Methods added by requiring "numru/netcdf_miss"

  - get_with_miss Same as get but interprets data missing.
  - get_with_miss_and_scaling Same as get_with_miss but handles data scaling too.
  - put_with_miss Same as put but interprets data missing.
  - put_with_miss_and_scaling Same as put_with_miss but handles data scaling too.

- class NetCDFAtt

  Class Methods

  Instance Methods

  - name Returns the name of the attribute
  - name= Rename the attribute
  - copy Copies an attribute to a variable or a file. If file, becomes an global attribute
  - delete Delete an attribute
  - put Sets the value of the attribute
  - get Returns the values of the attribute
  - atttype Inquires the type of attribute values
  - typecode Inquires the type of attribute values (returns a NArray typecode)

---------------------------------------------

# class NetCDF

### Class Methods

#### `NetCDF.open(filename, mode="r", share=false)`

  Opens a file (class method). If mode="w" and the file does not exist, a new file is created.

  Arguments

  - filename (String): file name (path)
  - mode (String) : IO mode "r" (read only); "w","w+" (write -- current contents are overwritten (eliminated!)); "r+","a","a+" (append -- writable while current contents are preserved). All the options permit reading, unlike the predefined File class. Note that to "append" will require extra time and disk space due to the limitations of the original NetCDF library, which is used in this library.
  - share (true or false) : Whether to use the "shared" mode or not (set true if a file being written may be read from other processes. See nc_open in Ch.5 of users' guide of the C version)

  Return value

  - a NetCDF object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_open, nc_create

#### `NetCDF.new`

  Aliased to NetCDF.open

#### `NetCDF.create(filename, noclobber=false, share=false)`

  Creates a NetCDF file (class method)

  Arguments

  - filename (String) : file name (path)
  - noclobber (true or false) : overwrite or not if the file exists
  - share (true or false) : Whether to use the shared mode or not (set true if a file being written may be read from other processes. See nc_open in Ch.5 of users' guide of the C version)

  Return value

  - a NetCDF object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_create

#### `NetCDF.create_tmp(tmpdir=ENV['TMPDIR']||ENV['TMP']||ENV['TEMP']||'.', share=false)`

  Creates a temporary NetCDF file (class method). Its name is automatically generated, and it is deleted when closed.

  Arguments

  - tmpdir (String) : directory to place the temporary file. By default, "." or a directory specified by an environmental variable (TMPDIR or TMP or TEMP) is used. In a secure mode, theses environmental variable is NOT used, and the default value is '.'.
  - share (true or false) : Whether to use the shared mode or not

  Return value

  - a NetCDF object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_create

### Instance Methods

#### `close`

  Closes the file.

  Arguments

  - (none)

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_close

#### `ndims`

  Returns the number of dimensions in the file

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_ndims

#### `nvars`

  Returns the number of variables in the file

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_nvars

#### `natts`

  Returns the number of global attributes in the file

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_natts

#### `unlimited`

  Returns the unlimited dimension in the file

  Arguments

  - (none)

  Return value

  - a NetCDFDim if it exists; nil if not

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_unlimdim

#### `path`

  Returns the path of the file (contents of the filename specified when opened/created)

  Arguments

  - (none)

  Return value

  - String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (none)

#### `redef`

  Switches to the define mode. Does nothing if already in it (nil returned).

  Arguments

  - (none)

  Return value

  - true if successfully switched to the define mode;

    nil if the file is already in the define mode.
    Exception is raised if unsuccessful for other reasons.

    Corresponding (dependent) function(s) in the C library of NetCDF
    *  nc_redef

#### `enddef`

  Switches to the data mode. Does nothing if already in it (nil returned).

  Arguments

  - (none)

  Return value

  - true if successfully switched to the data mode;

    nil if the file is already in the data mode.
    Exception is raised if unsuccessful for other reasons.

    Corresponding (dependent) function(s) in the C library of NetCDF
    *  nc_enddef

#### `define_mode?`

  Inquire whether the file is in the define mode.

  Arguments

  - (none)

  Return value

  - true if the data is in the define mode;

    false if the file is in the data mode;
    nil otherwise (possibly the file is read-only).

    Corresponding (dependent) function(s) in the C library of NetCDF
    *  combination of nc_redef and nc_enddef

#### `sync`

  Synchronizes the disk copy of a netCDF dataset with in-memory buffer

  Arguments

  - (none)

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_sync

#### `def_dim(dimension_name, length)`

  Define a dimension

  Arguments

  - dimension_name (String) : Name of the dimension to be defined
  - length (Integer) : length of the dimension. 0 for unlimited.

  Return value

  - defined dimension (NetCDFDim object)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_def_dim

#### `put_att(attribute_name, value, atttype=nil)`

  Sets a global attribute

  Arguments

  - attribute_name (String) : name of the global attribute
  - value (Numeric, String, Array of Numeric, or NArray) : value of the attribute
  - atttype (nil or String) : data type of the attribute value. nil lets it automatically determined from the value. "char" (or "string"), "byte", "sint", "int", "sfloat", or "float" specifies the type explicitly (1,1,2,4,4,8 bytes, respectively)

  Return value

  - created attribute (NetCDFAtt object)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_put_att_<type>

#### `def_var(name, vartype, dimensions)`

  Defines a variable

  Arguments

  - name (String) : Name of the variable to define
  - vartype (String or Fixnum) : data type of the variable ("char", "byte", "sint", "sint", "int", "sfloat", or "float"), or a NArray typecodes(Fixnum)
  - dimensions (Array) : Dimensions of the variable. An Array of NetCDFDim, in the order from the fastest varying dimension to the slowest varying one; its length becomes the rank of the variable.

  Return value

  - defined variable (NetCDFVar object)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_def_var

#### `def_var_with_dim(name, vartype, shape_ul0, dimnames)`

  Same as def_var but defines dimensions first if needed. Raise exception if it conflicts with the lengths of existing dimensions.

  Arguments

  - name (String) : Name of the variable to define
  - vartype (String) : data type of the variable ("char", "byte", "sint", "sint", "int", "sfloat", or "float")
  - shape_ul0 (Array of Integer) : Shape of the variable, i.e., lengths of dimensions. The unlimited dimension is specified by zero. The length of shape_ul0 determines the rank of the variable.
  - dimnames (Array of String) : Names of the dimensions. Its length (=>rank) must be equal to that of shape_ul0

  Return value

  - defined variable (NetCDFVar object)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (nc_def_var)

#### `var(var_name)`

  Opens an existing variable in the file

  Arguments

  - var_name (String) : Name of the variable to open

  Return value

  - a NetCDFVar object; nil if the variable does not exist

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_varid

#### `vars(names)`

  Opens existing variables in the file

  Arguments

  - names (nil or Array of String): Names of the variables to open; all variables are returned if nil (default).

  Return value

  - Array of NetCDFVar objects; exception is raised if names has a non-existent name

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_varid

#### `dim(dimension_name)`

  Opens an existing dimension in the file

  Arguments

  - dimension_name (String) : Name of the dimension to open

  Return value

  - a NetCDFDim object; nil if the dimension does not exist

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_dimid

#### `dims(names)`

  Opens existing dimensions in the file

  Arguments

  - names (nil or Array of String): Names of the dimensions to open; all dimensions are returned if nil (default).

  Return value

  - Array of NetCDFDim objects; exception is raised if names has a non-existent name

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_dimid

#### `att(attribute_name)`

  Opens an existing global attribute in the file

  Arguments

  - attribute_name (String) : Name of the global attribute to open

  Return value

  - a NetCDFAtt object if the attribute exists; nil if not

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (nc_inq_attid used for inquiry)

#### `fill=(filemode)`

  Sets a fill mode. (Default behavior of NetCDF is FILL.)

  Arguments

  - fillmode (true or false)

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_set_fill

#### `each_dim{ ... }`

  Iterator regarding the dimensions in the file. Ex.: {|i| print i.name,"\n"} prints names of all dimensions

  Arguments

  - { ... } : Block for the iterator. A "do end" block is the alternative.

  Return value

  - self

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_ndims)

#### `each_var{ ... }`

  Iterator regarding the variables in the file. Ex.: {|i| print i.name,"\n"} prints names of all variables

  Arguments

  - { ... } : Block for the iterator. A "do end" block is the alternative.

  Return value

  - self

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_nvars)

#### `each_att{ ... }`

  Iterator regarding the global attributes of the file. Ex.: {|i| print i.name,"\n"} prints names of all of them.

  Arguments

  - { ... } : Block for the iterator. A "do end" block is the alternative.

  Return value

  - self

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_natts, nc_inq_attname)

#### `dim_names`

  Returns the names of all dimensions in the file

  Arguments

  - (none)

  Return value

  - Array of NetCDFDim

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (nc_inq_ndims, nc_inq_dimname)

#### `var_names`

  Returns the names of all variables in the file

  Arguments

  - (none)

  Return value

  - Array of String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_nvars, nc_inq_varname)

#### `att_names`

  Returns the names of all the global attributes of the file

  Arguments

  - (none)

  Return value

  - Array of NetCDFAtt

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_natts, nc_inq_attname)

---------------------------------------------

# class NetCDFDim

### Class Methods

### Instance Methods

#### `length`

  Returns the length of the dimension

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_dimlen

#### `length_ul0`

  Same as length but returns 0 for the unlimited dimension

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_dimlen

#### `name=(dimension_newname)`

  Rename the dimension

  Arguments

  - dimension_newname (String) : new name

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_rename_dim

#### `name`

  Returns the name of the dimension

  Arguments

  - (none)

  Return value

  - String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_dimname

#### `unlimited?`

  Inquires whether the dimension is unlimited or not

  Arguments

  - (none)

  Return value

  - true or false

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_unlimdim)

---------------------------------------------

# class NetCDFVar

### Class Methods

#### `NetCDFVar.new(file,varname,mode="r",share=false)`

  open a NetCDF variable. This can also be done with NetCDF#var (instance method of NetCDF class), which is recommended over this method.

  Arguments

  - file (NetCDF or String) : a NetCDF file object (NetCDF) or the path of a NetCDF file (String).
  - varname (String) : name of the variable in the file
  - mode (String) : IO mode -- used if file is a String (see NetCDF.open)
  - share (true or false) : Whether to use the "shared" mode or not -- used if file is a String (see NetCDF.open)

  Return value

  - a NetCDFVar object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_open, nc_create, nc_inq_varid etc.)

#### `NetCDFVar.unpack_type=(na_type)`

  Fix the NArray type to be used in unpack.

  Arguments

  - na_type (Integer) : NArray::BYTE, NArray::SINT, NArray::INT, NArray::SFLOAT, or NArray::FLOAT

  Return value

  - na_type (the argument)

#### `NetCDFVar.unpack_type`

  Returns the NArray type set by NetCDFVar.unpack_type=.

  Return value

  - nil, NArray::BYTE, NArray::SINT, NArray::INT, NArray::SFLOAT, or NArray::FLOAT

### Instance Methods

#### `dim(dim_num)`

  Inquires the dim_num-th dimension of the variable (dim_num=0,1,2,..)

  Arguments

  - dim_num (Fixnum) : 0,1,... 0 is the fastest varying dimension.

  Return value

  - a NetCDFDim object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_vardimid)

#### `dims`

  Returns an array of all the dimensions of the variable

  Arguments

  - (none)

  Return value

  - Array of NetCDFDim objects.

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_vardimid

#### `shape_ul0`

  Returns the shape of the variable, but the length of the unlimited dimension is set to zero. Good to define another variable.

  Arguments

  - (none)

  Return value

  - Array. [length of 0th dim, length of 1st dim,.. ]

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_vardimid, nc_inq_unlimdim etc)

#### `shape_current`

  Returns the current shape of the variable.

  Arguments

  - (none)

  Return value

  - Array. [length of 0th dim, length of 1st dim,.. ]

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_vardimid etc)

#### `each_att{ ... }`

  Iterator regarding the global attributes of the variables. Ex.: {|i| print i.name,"\n"} prints names of all of them.

  Arguments

  - { ... } : Block for the iterator. A "do end" block is the alternative.

  Return value

  - self

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_natts, nc_inq_attname)

#### `dim_names`

  Returns the names of all the dimensions of the variable

  Arguments

  - (none)

  Return value

  - Array of String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_varndims, nc_inq_vardimid, nc_inq_dimname)

#### `att_names`

  Returns the names of all the attributes of the variable

  Arguments

  - (none)

  Return value

  - Array of String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (dependent on nc_inq_natts, nc_inq_attname)

#### `name`

  Returns the name of the variable

  Arguments

  - (none)

  Return value

  - String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_varname

#### `name=(variable_newname)`

  Rename the variable

  Arguments

  - variable_newname (String) : new name

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_rename_var

#### `ndims`

  Number of dimensions of the variable (which is rank of the variable).

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_varndims

#### `rank`

  Aliased to ndims

#### `ntype`

  Aliased to vartype

#### `vartype`

  Inquires the data value type of the variable

  Arguments

  - (none)

  Return value

  - String ("char","byte","sint","int","sfloat", or "float")

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_vartype

#### `typecode`

  Inquires the data type of the variable (returns a typecode of NArray)

  Arguments

  - (none)

  Return value

  - a Fixnum (NArray:BYTE, NArray:SINT, NArray:LINT, NArray:SFLOAT, NArray:SFLOAT, NArray:DFLOAT)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_vartype

#### `natts`

  Returns the number of the attributes of the variable

  Arguments

  - (none)

  Return value

  - Integer

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_varnatts

#### `file`

  Inquires the file that the variable is in

  Arguments

  - (none)

  Return value

  - a NetCDF object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (none)

#### `att(attribute_name)`

  Returns the attribute specified by its name

  Arguments

  - attribute_name (String) : Name of the attribute

  Return value

  - a NetCDFAtt object if the attribute exists; nil if not

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (nc_inq_attid is used for inquiry)

#### `put_att(attribute_name, value, atttype=nil)`

  Sets an attribute

  Arguments

  - attribute_name (String) : name of the attribute
  - value (Numeric, String, Array of Numeric, or NArray) : value of the attribute
  - atttype (nil or String) : data type of the attribute value. nil lets it automatically determined from the value. "char" (="string"), "byte", "sint", "int", "sfloat", or "float" specifies the type explicitly (1,1,2,4,4,8 bytes, respectively)

  Return value

  - a NetCDFAtt object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_put_att_<type>

#### `put(value, option=nil)`

  Aliased to simple_put

#### `simple_put(value, option=nil)`

  Set the values of the variable

  Arguments

  - value : value to set (Numeric, Array of Numeric (1D only), or NArray (possibly multi-D)). If it is a Numeric or length==1, the value is set uniformly.

  - option (Hash) : Optional argument to limit the portion of the variable to output values. If omitted, the whole variable is subject to the output. This argument accepts a Hash whose keys contain either "index" or a combination of "start","end", and "stride". The value of "index" points the index of a scalar portion of the variable. The other case is used to designate a regularly ordered subset, where "start" and "end" specifies bounds in each dimension and "stride" specifies intervals in it. As in Array "start", "end", and "index" can take negative values to specify index backward from the end. However, "stride" has to be positive, so reversing the array must be done afterwards if you like.

    Example: If the variable is 2D:

    {"start"=>[2,5],"end"=>[6,-1],"stride"=>[2,4]} -- Specifies a subset made as follows: the 1st dimension from the element 2 to the element 6 (note that the count starts with 0, so that the element 2 is the 3rd one) with an interval of 2; the 2nd dimension from the element 6 to the last element (designated by -1) with an interval of 5.

    {"index"=>[0,0]}: Scalar of the fist element

    {"index"=>[0,-2]}: Scalar from the 1st element of with respect to the 1st dimension and the 2nd element from the last with respect to the 2nd dimension

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_put_var_<type>, nc_put_vars_<type>, nc_put_var1_<type>

#### `pack(na)`

  Pack a NArray (etc) using the attributes scale_factor and/or add_offset of self.

  If scale_factor and/or add_offset is defined, returns (na-add_offset)/scale_factor. Returns na if not.

  Arguments

  - na : a numeric array to pack (NArray, NArrayMiss, or Array)

  Return value

  - a NArray or NArrayMiss

#### `scaled_put(value, option=nil)`

  Same as simple_put but interprets the attributes scale_factor and/or add_offset using pack.

  See the document for simple_put for arguments etc.

#### `get(option=nil)`

  Aliased to simple_get.

#### `simple_get(option=nil)`

  Returns values of the variable

  Arguments

  - option (Hash) : Optional argument to limit the portion of the variable to get values. Its usage is the same as in the method put.

  Return value

  - an NArray object

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_get_var_<type>, nc_get_vars_<type>, nc_get_var1_<type>

#### `unpack(na)`

  Unpack a NArray (etc) using the attributes scale_factor and/or add_offset of self.

  If scale_factor and/or add_offset is defined, returns na * scale_factor + add_offset. Returns na if not. Type conversion is made by the coercing -- for example if na is sint and scale_factor and add_offset is sfloat, return value is sfloat. The type of the return value can be specified explicitly with NetCDFVar.unpack_type=.

  Arguments

  - na : a numeric array to unpack (NArray, or NArrayMiss)

  Return value

  - a NArray or NArrayMiss

#### `scaled_get(option=nil)`

  Same as simple_get but interprets the attributes scale_factor and/or add_offset using unpack.

  See the document for simple_get for arguments etc.

#### `[]`

  Same as NetCDFVar#get but a subset is specified as in the method [] of NArray.

  In addition to the subset specifications supported by NArray, ranges with steps are supported, which is specified like {0..-1, 3}, i.e., a 1-element Hash with the key and value representing the range (Range) and the step (Integer), respectively. Unlike NArray, 1-dimensional indexing of multi-dimensional variables is not support.

#### `[] =`

  Same as NetCDFVar#put but a subset is specified as in the method []= of NArray.

  In addition to the subset specifications supported by NArray, ranges with steps are supported, which is specified like {0..-1, 3}, i.e., a 1-element Hash with the key and value representing the range (Range) and the step (Integer), respectively. Unlike NArray, 1-dimensional indexing of multi-dimensional variables is not support.

### Instance Methods added by requiring "numru/netcdf_miss"

#### `get_with_miss(option=nil)`

  Same as get but interprets data missing.

  Data missing is specified by the standard attributes valid_range, (valid_min and/or valid_max), or missing_value, with the precedence being this order. Unlike the recommendation in the NetCDF User's guide, missing_value is interpreted if present. If missing_value and valid_* present simultaneously, missing_value must be outside the valid range. Otherwise, exception is raised.

  If data missing is specified as stated above, this method returns a NArrayMiss. If not, it returns a NArray. Thus, you can use this whether data missing is defined or not.

  Arguments

  - See get.

  Return value

  - an NArrayMiss (if data missing is specified) or an NArray (if data missing is NOT specified)

  Possible exception in addition to NetcdfError.

  - missing_value is in the valid range (see above).

  Corresponding (dependent) function(s) in the C library of NetCDF

  - See get. This method is written in Ruby.

  EXAMPLE

  - The following is an example to replace get with get_with_miss. It will also make [] interpret data missing, since it calls `get` internally.

        file = NetCDF.open('hogehoge.nc')
        var = file.var('var')
        def var.get(*args); get_with_miss(*args); end
        p var.get       # --> interprets data missing if defined
        p var[0..-1,0]  # --> interprets data missing if defined (assumed 2D)

#### `get_with_miss_and_scaling(option=nil)`

  Same as get_with_miss but handles data scaling too using unpack.

  Missing data handling using valid_* / missing_value is applied basically to packed data, which is consistent with most conventions. However, it is applied to unpacked data if and only if the type of valid_* / missing_value is not the same as the packed data and is the samed as the unpacked data. This treatment can handle all conventions.

  EXAMPLE

  - See above. The same thing applies.

#### `put_with_miss(value, option=nil)`

  Same as put but interprets data missing.

  If `value` is an NArray, the methods behaves as put. Data missing in `value` is interpreted if it is an NArrayMiss and data missing is specified by attributes in `self` (see get_with_miss ). Namely, the data which are "invalid" in the `value` is replaced with a missing value when written in the file. (missing_value or _FillValue or a value outside the valid range). No check is made whether "valid" values in the NArrayMiss is within the valid range of `self`.

  Arguments

  - value : NArrayMiss or what is allowed in put.
  - option (Hash) : See put.

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - See put. This method is written in Ruby.

  EXAMPLE

  - The following is an example to replace put with put_with_miss. It will also make []= interpret data missing, since it calls `put` internally.

        file = NetCDF.open('hogehoge.nc')
        var = file.var('var')
        def var.put(*args); put_with_miss(*args); end
        var.put = narray_miss      # --> interprets data missing if defined
        var[0..-1,0] = narray_miss # --> interprets data missing if defined (assumed 2D)

#### `put_with_miss_and_scaling(value, option=nil)`

  Same as put_with_miss but handles data scaling too using pack.

  Missing data handling using valid_* / missing_value is applied basically to packed data, which is consistent with most conventions. However, it is applied to unpacked data if and only if the type of valid_* / missing_value is not the same as the packed data and is the samed as the unpacked data. This treatment can handle all conventions.

  EXAMPLE

  - See above. The same thing applies.

---------------------------------------------

# class NetCDFAtt

### Class Methods

### Instance Methods

#### `name`

  Returns the name of the attribute

  Arguments

  - (none)

  Return value

  - String

  Corresponding (dependent) function(s) in the C library of NetCDF

  - (none)

#### `name=(attribute_newname)`

  Rename the attribute

  Arguments

  - attribute_newname (String) : New name

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_rename_att

#### `copy(var_or_file)`

  Copies an attribute to a variable or a file. If file, becomes an global attribute

  Arguments

  - var_or_file (NetCDFVar or NetCDF)

  Return value

  - Resultant new attribute (NetCDFAtt)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_copy_att

#### `delete`

  Delete an attribute

  Arguments

  - (none)

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_del_att

#### `put(value, atttype=nil)`

  Sets the value of the attribute

  Arguments

  - value (Numeric, String, Array of Numeric, or NArray) : value of the attribute
  - atttype (nil or String) : data type of the attribute value. nil lets it automatically determined from the value. "char" (="string"), "byte", "sint", "int", "sfloat", or "float" specifies the type explicitly (1,1,2,4,4,8 bytes, respectively)

  Return value

  - nil

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_put_att_<type>

#### `get`

  Returns the values of the attribute

  Arguments

  - (none)

  Return value

  - String or an NArray object (NOTE: even a scalar is returned as an NArray of length 1)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_get_att_<type>

#### `atttype`

  Inquires the type of attribute values

  Arguments

  - (none)

  Return value

  - "char","byte","sint","int","sfloat","float"

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_atttype

#### `atttype`

  Inquires the type of attribute values (returns a NArray typecode)

  Arguments

  - (none)

  Return value

  - a Fixnum (NArray:BYTE, NArray:SINT, NArray:LINT, NArray:SFLOAT, NArray:SFLOAT, NArray:DFLOAT)

  Corresponding (dependent) function(s) in the C library of NetCDF

  - nc_inq_atttype