RubyNetCDF Reference Manual

Index

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Overview

RubyNetCDF is the Ruby interface of the NetCDF library. Ruby is a free object-oriented scripting language and is available from http://www.ruby-lang.org/. To handle numeric data, RubyNetCDF uses NArray, which is the standard numeric multi-dimensional array class for Ruby (http://www.ruby-lang.org/en/raa-list.rhtml?name=NArray). 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.

Structure

RubyNetCDF consists of the four class 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.

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 returns 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.

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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.

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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)
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.
- enddef Switches to the data mode. Does nothing if already in it.
- 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
- var Opens an existing variable in the file
- dim Opens an existing dimension 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
- name= Rename the dimension
- name Returns the name of the dimension
- unlimited? Inquires whether the dimension is unlimited or not
class NetCDFVar

Class Methods

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
- 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).
- ntype
- vartype Data value type of the variable
- 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 Set the values of the variable
- get Returns values of the variable
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

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class NetCDF

Class Methods

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

Opens a file (class method). If mode="w" and non-existent, a new file is created.

Arguments

filename (String): file name (path)
mode (String) : IO mode "r"(read only), "w"(writable)
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) : sharedにするか

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

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.

Arguments

(none)

Return value

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

nc_redef

enddef

Switches to the data mode. Does nothing if already in it.

Arguments

(none)

Return value

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

nc_enddef

sync

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

Arguments

(none)

Return value

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. "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(variable_name, vartype, dimensions)

Defines a variable

Arguments

variable_name (String) : Name of the variable to define
vartype (String) : data type of the variable ("byte", "sint", "sint", "int", "sfloat", or "float")
dimensions (Array) : Dimensions of the variable. An Array of NetCDFDim, in the order from the fastest varying dimension to the slowliest 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

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 if the variable exists; nil if not

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 if the dimension exists; nil if not

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

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)

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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

name=(dimension_newname)

Rename the dimension

Arguments

dimension_newname (String) : new name

Return value

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)

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class NetCDFVar

Class Methods

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

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

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

ntype

vartype

Data value type of the variable

Arguments

(none)

Return value

String ("string","byte","sint","int","sfloat", or "float")

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. "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)

Set the values of the variable

Arguments

value : value to set (Numeric, Array of Numeric (1D only), or NArray (possibly multi-D))
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

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

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

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>

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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

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

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. "string", "byte", "sint", "int", "sfloat", or "float" specifies the type explicitly (1,1,2,4,4,8 bytes, respectively)

Return value

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

"string","byte","sint","int","sfloat","float"

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

nc_inq_atttype