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Package Descriptions

ncview
FERRET
NCAR Graphics
GrADS
tkgrads

ncview

DESCRIPTION :

Ncview is a visual browser for netCDF data format files. Ncview displays a 2-dimensional, color representation of single precision floating point data in a netCDF file. You can animate the data in time (making simple movies), flip or enlarge the picture, scan through various axes, change colormaps, etc. Ncview is *not* a plotting program or an analysis package. Rather, its purpose in life is to view data stored in netCDF format files quickly, easily, and simply.

PLUSES :

- short user spin-up

- fast cross-sectioning

- magnification capability

- a number of predefined color palettes, which can be inverted and "scrunched" to highlight high or low values

- animation (along least quickly varying dimension only)

- print capability

- can take a series of files as input (ie, sequence of snapshot history files)

- mouse <left-click> pops up a time-series graph for variables at that point

- animation speed control

- mouse-selectable colormap endpoints, with optional reset

- Optional Map overlay

- Option to filter out 1-D variables ("-no1d")

 

MINUSES :

- no contour lines or vectors

- no legend/labelbar, axis/tic-marks, geography

- will not do X-Z or Y-Z crossections unless there is a 4th ("time") dimension

- does not handle unpacking of "packed" (8- or 16-bit) data

- the coordinate label for the "scan dimension" can lack precision depending on how UDUNITS is used to create a "friendlier" label; the actual coordinate value is correctly displayed in the plot window.

- overlaid map can get messed up if you switch to a varible with a different horizontal grid ---simply turn the overlay "Off" then back "On"

HOW TO INVOKE :

• Note: ncview should almost always be run on a workstation, but you may occasionally need it to view files in FTMPDIR, for example.
• You may wish to slightly modify the X-resources for ncview. In particular, some things like fonts, background colors and button sizes should be adjusted. There are two ways to do this:
1. (Recommended) Place the following line in your /home/$user/.Xdefaults file, although Ncview 1.93 now supports collapsed variable lists:

       Ncview*nVarsPerRow: 10
   

2. You can also edit the ncview resources file (/usr/lib/X11/app-defaults/Ncview) to personalize the look of ncview in many more ways.
• You might also want to be able to access a couple of user-defined ncview colormaps that do not come with the main distribution. To do this, enter (or add to one of your ~/.login files):
• setenv NCVIEWBASE /home/$user/my_ncview_colormaps
Next, create yourself an alias for ncview (perhaps in one of your ~/.cshrc files):
alias ncview 'ncview -extrainfo -minmax med -private'
• Startup ncview by entering :
• ncview [nc_file]

HINTS :

• <left-click> at any point in the plot to get a graph of the variable vs. time at that point.
• <Ctrl><left-click> at any point to set the colormap minimum to the value at that point.
• <Ctrl><right-click> at any point to set the colormap maximum to the value at that point.
• Use the "Range" button to set (or reset) the colormap min/max

INFO / DOCUMENTATION :

• There is an ncview "man" page
• URL/Web

FERRET

DESCRIPTION :

FERRET is an interactive computer visualization and analysis environment designed to meet the needs of oceanographers and meteorologists analyzing large and complex gridded data sets. FERRET can be used to analyze the outputs of its numerical ocean models and compare them with gridded, observational data. The model data sets are generally multi-gigabyte in size with mixed 3 and 4-dimensional variables defined on staggered grids.

FERRET offers a Mathematica-like approach to analysis; new variables may be defined interac tively as mathematical expressions involving data set variables. Calculations may be applied over arbitrarily shaped regions. Fully documented graphics are produced with a single command. Ferret provides well-proven scientific graphics styles, such as contours, scatter plots, and vector diagrams, and the ability to define new variables as mathematical expressions involving data base variables. Analysis is augmented by regridding capabilities and boolean operators to per form calculations over arbitrary regions. Ferret's data management is based on a simple, adapt able data model incorporated into standardized, self-describing, direct-access files.

ADDITIONAL INFORMATION:

• FERRET can produce animation files, but they are in HDF format. The only tool available at GFDL for viewing these files is NCSA's XDataSlice, an ancient package that has not been supported since 1993, will not work under Irix 6, and cannot be rebuilt because it uses extinct widget libraries. Nevertheless, for now, it works! (See also gif2flc below.)

• To use XDS, first edit your ~/.Xefaults file to add the the contents of ~jps/pub/app-defaults/XDS, which looks like this:

  
       !# X DataSlice resources
  
       !# Append this file to the end of the .Xdefaults file in your home directory.
  
       !# The following resources may also be set to TRUE using the command line
  
       !# options at the start of the program, eg. xds -installCMap will turn on
  
       !# the resource installCMap to TRUE.
  
       !#   inputFocus - set this to TRUE if your input focus is not accepted in
  
       !#      any dialog widget in XDS. Default is FALSE.
  
       !#   adjustToggles- set this to TRUE if the toggles appear to be too large
  
       !#      as to occlude other toggles in the window. This happens
  
       !#      on some clients like the Cray2, HP and sun386i.
  
       !#      Default is FALSE.
  
       !#   installCMap - set this to TRUE ONLY if the color map is not set when
  
       !#      it should be. This happens on clients such as the IRIS
  
       !#      and on some window managers. Default is FALSE.
  
       !#   useXImage - set this to TRUE if you wish the the animation windows to
  
       !#      use XImages instead of Pixmaps to store images as default.
  
       !#      If it is FALSE, the animation windows will use Pixmaps.
  
       XDS*inputFocus:    TRUE
  
       XDS*adjustToggles: TRUE
  
       XDS*installCMap:   TRUE
  
       XDS*useXImage:     FALSE
  
       XDS*XDSlabel.foreground:  blue
  
       XDS*XDSlabel.background:  white
  
       XDS*XDSbutton.foreground: red
  
       XDS*XDSbutton.background: white
  
       !# Do not change
  
       XDS*input: TRUE
  
       XDS*font: 6x13
  
       XDS*XDSbox.borderWidth: 1
  
       XDS*XDSbox.borderColor: black
  
       XDS*XDSbulletin.borderWidth: 1
  
       XDS*XDSbulletin.borderColor: black
  
  

• To run XDS, enter:

  
       /net/jps/ftp/ftp.ncsa.uiuc.edu/UNIX/XDataSlice/XDS2.2/XDS2.2.sgi
  
  

  When the XDataSlice window pops up, press the "Load 8-bit RASTER" button to select the HDF movie. Then press the "ANIMATE RASTERS" button to view the file. You can navigate through the animation with the arrow buttons in the control panel at the bottom of the window.
  
  If you are running on a SGI 4D/25 or 4D/35, you may experience colormap problems. To put XDS in contol of the colormap, click on the XDS window title-bar while holding down the <Alt> key. To return control to another application, press <Alt> and click on its title bar.

• You can also use the GIF file output capability of FERRET to produce animations. After you save the series of GIF files, run /home/jps/pub/graphics/gif2flc (or emulate the processes that the gif2flc C-shell script goes through) to create a (deprecated) FLC animation file that is playable with xanim.

• USAGE:

     gif2flc first.gif last.gif file_prefix_ [red_factor] filename.flc

• * It is assumed that the main body of the animation is built from files with the sequence number coded into the filename, eg, 'file_prefix_001.gif', so that /bin/ls yields the proper order.

 
• 'first.gif' and 'last.gif' are specified separately to create dwells at the ends, and because 'first.gif' often has a name (eg, 'intro.gif') that is not part of the sequenced names.

 
• Example:

gif2flc intro.gif my_anim_060.gif my_anim_ my_anim.flc

• Note: The size of the picture is taken from file 'first.gif'. The (optional) reduction factor must be an integer (ie, 2 => half-size)

INFO / DOCUMENTATION :

• User's Guide
• Project Homepage
• Andrew Wittenberg's Notes

NCAR Graphics

DESCRIPTION :

NCAR Graphics is a collection of graphics libraries that supports the display of scientific data via contours, area-fill, map overlays, X-Y plots, etc.

PLUSES :

- plots are customizable to the N-th degree (NCARG's claim to fame)

- supported by a major development group with a long history and stable funding
- the "idt " metafile viewer is very versatile, and supports flipbook animation
- the new approach of setting "resources" and then "realizing" the plot is less error prone than the traditional subroutine-calling approach

MINUSES :

- GUI promised in early '96 and prototyped up until version 4.1.x

- NCL is much wordier (albeit more informative) than, say, GrADS or MATLAB
- the GUI is quite nominal :

officially, overlays (eg, ezmaps) are not supported (though I've done it...)

data ingestion is only via NCL

officially, no way to manipulate colormap (though I've done this, too, to some extent)

no way to save the "state" of a plot (fix promised for early '96)

HOW TO INVOKE :

1. Make sure your environment variables point to NCARG:

   # Linux x86 
   setenv NCARG_ROOT /usr/local/ncarg-4.3.1
   setenv NCARPATH /usr/local/ncarg-4.3.1/bin
   setenv PATH $:$
   
   # Linux ia64
   setenv NCARG_ROOT /usr/local/ncg/ncarg-4.4.1
   setenv PATH $:$/bin
   

2. Startup NCL by entering :

   
        ncl
   
   

HINTS :

Take a look at the following "starter" NCL scripts :

- test2.ncl : contains some basic NCL that you can "select and paste" into the window where you are running NCL

- basic_fns.ncl : some basic NCL functions used to set map characteristics, adjust colors, perform contouring

- startx.ncl : used by "test2.ncl" to intialize an X-window, as well as a map, data, and contour "objects"

- for_gui.ncl : contains some basic NCL that you can "select and paste" into the NCL Editor window of the GUI to get things started (setting colomaps, creating map/contour/data/text objects; also include sample NCL to access data files, take slices, overlay maps, etc.)

INFO / DOCUMENTATION :

• man page
• User's Guide (The index is very helpful)
• URL/Web info
• Summary of some tools

GrADS

DESCRIPTION :

The Grid Analysis and Display System (GrADS) is a command-line tool for accessing, manipulating, and displaying data on a variety of computer platforms. A scripting language also makes it suitable for batch applications. Gridded (or station) data is located within a 4-Dimensional space (usually longitude, latitude, level, and time) through a data description file. GrADS suports the UNIX byte-stream and GRIB data formats, and ingestion of NetCDF data is (minimally) available beginning with version 1.6 (beta).

Data may be displayed using a variety of graphical output techniques, including contours, shading, vectors, scatter plots and geography. VCS can also be used to plot GrADS-compatible data.

PLUSES :

- animation of 2-D plots

- plots are very customizable
- mathematical manipulation / user function capability
- reads GRIB data
- reads netCDF data (though very nominally)
- reads and plots station data

MINUSES :

- GrADS' data format is supported by a very limited number of packages

- GrADS' data format handles only one grid per file (e, no staggered grids)

NOTE :

GrADS data files generated on Intel-based platforms (PC`s) will be "byte-swapped", i.e., the byte ordering is different. You will need to insert an "OPTIONS BYTESWAPPED" line in the control file. To use the data file in other codes, you can make a copy of the file with the bytes reordered using the byteswap utility.

For more complete information, see Tony Gordon's GrADS Page.

XGrads (tkgrads)

DESCRIPTION

XGrads is a graphical interface for the GrADS program written in the Tcl/Tk language. It provides point-and-click accessibility to most of the capabilities of GrADS, thereby almost eliminating the need for typing in commands. XGrads does not modify GrADS in any way, but just acts as a front-end passing information back and forth between its GUI and the command-line GrADS. All widget settings can be saved so plots are easily reproducible.

Note: Although the program is officially called XGrads, the startup script has been renamed to tkgrads in order to avoid filename conflicts and emphasize it's graphical capability.

PLUSES

• Fairly simple and intuitive.
• All widget settings can be saved for later use.
• All GrADS commands can be manually entered if necessary.

MINUSES

• The widget settings only apply to the variables listed in a description or control file. Variables defined interactively can only be manipulated from the command window.
• Can only work with one plot window at a time.
• Doesn't seem to work with GrADS 1.7 beta 9, although it does with 1.7 beta 7.
• Will not read netCDF files even though newer versions of GrADS will.

HOW TO INVOKE

In order to use tkgrads, first set up the environment variables and the path as described on the GrADS page. Be sure to replace all occurrances of "beta9" with "beta7" if a newer version of GrADS is preferable. Then run the program:

     /home/hnv/pub/irix/tcl/XGrads/tkgrads

DOCUMENTATION

• PostScript description (gzip-compressed, GFDL only)
• HTML description (GFDL only)

 

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