Scripting Guide - SAS

Chapter 9 Data Tables 235
Data Table Basics
Data Table Basics
JSL has full access to the values and properties of a data table. This section examines how to open and close
data tables, view their properties, and interact with their data.
Once you have a data table open, you accomplish most other data tasks by sending messages to a reference
to the data table object. Objects acting on messages is a common theme in this book. As soon as you see
how to create or open a data table object, step back and look at how objects and messages work.
Getting a Data Table Object
Any of the following methods of beginning to work with a data table produces a data table object.
Opening a Data Table
Opening a data table returns a reference to the data table. Usually, you assign the reference to a variable for
later use. The usual argument for Open is a path (either relative or absolute) to the data table. For
information about using POSIX filenames and the built-in path variables, see “Path Variables” on page 105
in the “Types of Data” chapter.
Open("$SAMPLE_DATA/big class.jmp"); // just open the data table
dt=Open("$SAMPLE_DATA/big class.jmp"); // open and assign a reference
The path can be a literal path (absolute or relative) in quotation marks or an expression yielding a
pathname. Relative paths are interpreted relative to the location of the .JSL file (if the script has been saved)
or the JMP application (for an unsaved script); use ../ to move up one folder level. Example scripts
typically use a relative path to open files from the installed Sample Data folder. You can also use the Set
Current Directory command.
If no arguments are given, Open presents a window prompting the user to navigate to a file.
If a data table with that path is already open, then JMP does not read it again but instead brings that
window in the front. If you have made changes, then the table is not the same as the one on disk that you
might expect. Since JMP always keeps the whole table in memory, opening is equivalent to reading the
whole file.
Test for an Open Data Table
In a script that depends on an opened data table, test to see whether the table is open using Is Empty() or
Is Scriptable(). In the following example, the script performs a Bivariate analysis on Big Class.jmp
and then closes the data table. Before proceeding to the Oneway analysis later in the script, If
Scriptable() tests for the open data table. If 0 is returned, the table opens, and the script continues.
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
obj = Bivariate( Y( :height ), X( :age ), Fit Line );
Close( dt );
...
If(
Is Scriptable ( dt ), 0,