GitHub - tenomoto/ncl-read_grads: Awk scripts and a ncl script to read GrADS ctl files

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Awk scripts and a ncl script to read GrADS ctl files

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Name		Name	Last commit message	Last commit date
Latest commit History 2 Commits
ChangeLog		ChangeLog
README		README
dset.awk		dset.awk
grads.ncl		grads.ncl
tdef.awk		tdef.awk
test.ncl		test.ncl
title.awk		title.awk
undef.awk		undef.awk
vardescs.awk		vardescs.awk
varid.awk		varid.awk
varlevs.awk		varlevs.awk
varnames.awk		varnames.awk
xdef.awk		xdef.awk
ydef.awk		ydef.awk
yrev.awk		yrev.awk
zdef.awk		zdef.awk
zrev.awk		zrev.awk

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*Scripts for parsing GrADS .ctl files

-Author: Takeshi Enomoto
-History: 
  18 Aug 2005 v0.3: bug fix. hours were obtained incorrectly
  25 Feb 2005 v0.2: bug fixes. grads_time() now returns a useful array
  22 Feb 2005 v0.1: first release

This suites consists of awk and ncl scripts.

*awk scripts
**scripts to read file meta information:

	-dset.awk: returns the path to the data file
	-title.awk: returns the title
	-undef.awk: returns the undefined value

**scripts to read coordinates and their meta information:

	-xdef.awk: returns x coordinates
	-ydef.awk: returns y coordinates 
	-yrev.awk: returns -1 if option yrev is found 1 if not
	-zdef.awk: returns z coordinates
	-zrev.awk: returns -1 if option zrev is found 1 if not
	-tdef.awk: returns number of records, units, and increment

**scripts to read variables meta information:

	-varnames.awk: returns variable names
	-varlevs.awk: returns the number of levels for each variable
	-vardescs.awk: returns the description (long name) for each variable
	-varid.awk: returns the place of a give variable name in all variables

*ncl utility script

**grads.ncl

Install .awk and .ncl scripts to appropriate directory.
Here it is assumed that they are installed in:
	$HOME/lib/ncarg/nclscripts/grads/

To use this script first load this script before "begin" statement.

	load "$HOME/lib/ncarg/nclscripts/grads/grads.ncl"

To read meta data use grads_addfile() function.
It simply returns the name of the input but with meta data
such as coordinates as attributes.

		f = grads_addfile("path/to/your/control/file.ctl")

Available attributes are:

	-grd: path to the data file ("DSET")
	-title: "TITLE"
	-undef: "UNDEF"
	-lon: x coorinates
	-lat: y coorinates
	-lev: z coorinates
	-varnames: names of variables
	-varlevs: the number of levels for each variable
	-vardescs: description (long name) of each variable
	-offsets: offset of each variable from the start of the record
	-nlevs: total number of levels per record

Function grads_read() returns a 2D or 3D array at a record:

		x = grads_read(f,f@varnames(0),0)

Function grads_time() returns an array of increments from the initial time
with units as attributes

*Limitations
Parsing is not perfect so there are a numbers of limitations in particular:
-Byte reversing is not supported.
-mixed case such as Xdef, xDef are not supported (xdef, XDEF are OK)