Scripting Guide - SAS

240 Data Tables Chapter 9
Data Table Basics
Note: To prevent “lost” data tables created invisibly, you can create an invisible data table only if you assign
it a reference. If you do create an invisible data table without a reference, JMP immediately destroys it, so
any further uses of the table result in errors.
Tip: Once you are finished with an invisible data table, do not forget to close it. Otherwise, it remains in
memory until you quit JMP.
Objects and Messages
Many JMP capabilities are performed by scriptable objects within JMP that know how to execute tasks
relevant to themselves. Objects are entities that, once created, know how to do certain things for themselves.
A JMP data table is one such object.
To work with an object from JSL, you send a message to the object, asking it to perform one of its tasks.
Messages are commands that can be understood only in context by a particular type of object. For example,
messages for data table objects include Save, New Column, Sort, and so on. Most of these would not make
any sense for a platform object, for example.
Each object defines its own set of messages and what those messages mean. Although there might be some
messages that happen to exist for more than one type of object, each message’s effect is determined solely by
that object. This is one way in which JSL is heavily context-dependent.
First, you see how to address a data table object with a reference, then how to send a message to the reference,
and then learn about the messages data table objects can understand. A later section examines another type
of object, data table columns. Subsequent chapters explore analysis and graph platform objects, display
objects, and others.
Storing a Reference to a Data Table
To review, here are the various ways to get a data table open. Notice that each expression begins with an
assignment to a variable. That is because each of these expressions, in addition to creating or opening the
data, returns a value that is a reference to the table (a reference to a scriptable object). By assigning the data
table reference to a global variable, you can use that variable to talk to the object. (This manual uses the
placeholder dt to represent data table references.)
dt=open("..\sample data\big class.jmp"); //Windows
dt=open("::sample data:big class"); //Macintosh
dt=open("$SAMPLE_DATA/Big Class.JMP"); // all operating systems
dt=new table("myTable"); // create a new data table
You can also assign a reference to a table you already have open, in case you did not include an assignment in
your Open or New Table statement (or if you opened it through the menus):
dt=data table("myTable"); // the open table named myTable
dt=current data table(); // the table in the topmost window
dt=data table(3);
// the third open table
Current Data Table can also take a scriptable object reference as an argument. For example, this would
make current the data table in use by the second Bivariate object:
Current Data Table(Bivariate[2]);