Using JMP - SAS

Chapter 5 Set Column Properties 163
Assign a Preselected Analysis Role
Assign a Preselected Analysis Role
You can assign an analysis role, such as x, y, weight, or frequency, to a selected column and save the role with
the data table. When you do this and then run an analysis, JMP uses the preselected role to automatically fill
in the role boxes in windows. Then you do not have to specify these roles each time you run an analysis. For
example, you might want a column named height to take the x role in every analysis of that data table. To
enforce the x role, you assign the preselected role of x to the column.
When you select Freq, the values in that column are what JMP uses as the frequency of the observation. If n
is the value of the Freq variable for a given row, then that row is used in computations n times. If it is less
than 1 or is missing, then JMP does not use it to calculate any analyses.
When you select Weight, the values in that column provide weights for each observation in the data table.
The variable does not have to be an integer, but it is included only in analyses when its value is greater than
zero.
To assign a preselected role to a column:
1. Highlight the column.
2. Select Cols > Preselect Role.
3. Select a role: No Role, X, Y, Weight, or Freq.
After you select the appropriate roles, icons in the Columns panel signify what roles have been assigned.
Click the icon to access a list of roles and select a different one. See “Icons Representing Column
Characteristics and Properties” on page 37 in the “Get Started” chapter.
Compress Selected Columns
JMP lets you compress columns in a data table to minimize the size of the file and reduce the amount of
memory required to analyze data. This feature is helpful when numeric columns contain many small
integers or when any column contains fewer than 255 unique values. For example, compressing columns in
a data table with 389 columns and 85,000 rows might decrease the file size from 250MB to 33MB,
depending on the type of data.
When you compress columns, JMP verifies whether the data can be stored in a more compact form based
on the data type:
• In character columns with fewer than 255 unique values, the List Check property is added to the
column (shown in Figure 5.6).
• In numeric columns, data is compressed to 1-byte, 2-byte, or 4-byte integers when possible (shown in
Figure 5.7). For details about short integers, see “The Short-Integer Format” on page 145.
A numeric column with non-integer values can also be compressed if there are fewer than 255 unique
values. In this case, the List Check property is added to the column.