CDFx is an IDL software tool for displaying, editing, and listing the contents of CDF data files. It displays image plots, time-series plots, CDF variables; it will list and store CDF data in plain ASCII text; and it will save subsets of data to new CDF files.

Familiarity with CDF and ISTP CDF conventions will be helpful when using CDFx. ISTP specifications and master CDF file concept discussions are at the SPDF Use of CDF site. General discussion of the CDF data format can also be found on the CDF site.

Downloading and Running

CDFx is a part of CDAWlib and requires that Harris' IDL, versions 8.3 or newer, be installed on your local system. IDL8.3 and newer versions, both 64 and 32 bit versions should work, but require the fixes to the CDF API s/w which are available from the CDF site:, specific information is at It is not necessary to compile or run any of CDAWlib's other tools in order to use CDFx.

After downloading and installing CDAWlib, and after following the General Instructions in CDAWlib's on-line help, CDFx should be ready to run. Launch an IDL session and enter the following commands (displayed in boldface):

IDL> @compile_cdfx
% Compiled module: VERSION.
% Compiled module: CDFX.
IDL> cdfx

You should now see CDFx's main menu window, which will remain on your desktop throughout the CDFx session.

Quick Tutorial

This section demonstrates a simple CDFx session that illustrates some of the software's key features.

  1. First, launch CDFx as shown above.

  2. Next, download some sample CDF data files to play with ( here and here ), and optionally load the master file that goes with them. Put all these files into your current working directory.

  3. Click on the Read CDF files button in the CDFx menu window. A standard file dialog box will appear, for you to choose the CDF files you are interested in. You should be able to control-click or shift-click on the names to make a multiple-file selection. Select the two data files you downloaded earlier.

  4. A new dialog box will appear, for you to select the CDF variables you are interested in. For this tutorial, select IMAGE_DATA and GCI_LOOK_DIR, then click the Proceed button.

  5. Some time may pass while CDFx processes the files and extracts the variables. (You should see an "hourglass" cursor during this processing.) Eventually, a CDFx object window will appear, which represents the set of data you've chosen to work with. The top portion shows general information about the object, the middle portion shows the object variables that are available, and the lower portion contains buttons for invoking actions.

  6. Select the IMAGE_DATA variable by clicking on its name. Then, under the Variable Actions pull-down menu, invoke the Plot Variable command to bring up a CDAWlib plot of the variable. Similarly, you can plot the GCI_LOOK_DIR variable. You should see windows resembling this and this.

  7. You might also try the Show/Edit vattrs command under the same menu, after selecting any of the variables. This will show its contents, size, type, and various descriptive information.

  8. Use the Time Filter command if desired to narrow the time interval covered by the object. This will create a new CDFx object, in a new window, representing the restricted subset of the original data.

  9. Use the Save Object command to store the current object into an IDL save file, or into a new CDF data file.

  10. Use the List Variable command to dump a variable's content into a plain ASCII text file. (It is probably unwise to invoke this command on images or other large variables. Try it instead on the GCI_LOOK_DIR variable.) At present, list files are automatically stored in your current working directory, with a file name taken from the variable's name.

  11. When you wish to leave CDFx, click the Quit button in the main menu window. Before doing this, you can choose to save each object individually -- or as an alternative you can save all objects simultaneously with the Save Data Objects button. This will create IDL ".sav" files in the current working directory. Next time you run CDFx, you can restore all the objects at once by using the Restore Data Objects button.

Responsible NASA Official:
Robert McGuire, (301) 286-7794
Head of Space Physics Data Facility
NASA Goddard Space Flight Center
Greenbelt MD 20771
CDAWeb Curators

Last update: 2017-Jun-5