Overview of Data Access in IDL

There are several ways to open files and access the data that they contain in IDL.You can open a file using interface elements, or using routines. In order of increasing complexity and flexibility, your options are:

Accessing data in iTools — use File

Open from an iTool, and browse to select a file. This option automatically displays data (that is a supported type) in the iTool. See Importing and Exporting Data for details.

Accessing files using dialogs — launch an IDL dialog and browse to select or save a file. After accessing the file, use an IDL routine to access the data within the file. You can then preform additional data processing task or create a display. See Accessing Files Using Dialogs for details.

Accessing files programmatically — you can access data without requiring user interaction by using IDL statements in a program or at the command line. This give you the greatest control over the state of data at all times, but requires slightly more programming than the previous option. See Accessing Files Programmatically for details.

There are advantages and disadvantages for each option. When you open a file using File

Open in the iTools, there is no opportunity to do pre-processing on the data. However, the display is created for you, and there are numerous interactive operations available.

When you access data from the command line or in an IDL program, you have the greatest control over data modification. The iTools incorporate the functionality of many of the common data processing and manipulation routines. However, if you need greater control over data modification, want to create a custom display or object class, or need to use functionality that is not exposed through and iTool, you can import, export, and/or create your data programmatically.

Regardless of the method selected, it is important to note that only the options involving iTools will automatically display data for you. In other instances, you will need to configure a display yourself.