Basic data operations in SPSS - ISS - University of Leeds

Basic data operations in SPSS for Windows 17
Version 6 (November 2009)
Note: If a column displays asterisks (*****), simply widen the column to see the data. This can
be done by pointing the mouse to the boundary between the cells, and dragging to the right
when the mouse pointer changes to a double headed arrow.
Figure 44: Widening the column width
A practical consideration in performing a merge is the order in which the two files are specified.
They can be specified in either order, but the choice is important because it can affect the
variable definitions assigned to common variables in the merged file. For example, if a numeric
variable common to both files has a decimal places value of 0 in the active file and 2 in the file
being added, the value assigned in the merged file would be 0. If the active file is our master
file, then this might be acceptable. But if the file being added was our master file, then this
would probably not be acceptable since it would mean that we are over-riding definitions which
we have laid down in our master file.
The conclusion might be, therefore, to always open the master file first and to add cases from
the second file. Whilst this would prevent the possibility of master definitions being changed, it
would also prevent us from changing any other definitions in the active file prior to the merge.
Accordingly, in this example, we have chosen to open the file containing the new cases first so
that we can change the active file prior to the merge. This approach does require, of course,
that care is taken to ensure that master definitions are not inadvertently changed. The motto
must therefore be: caution.
Task 14 Adding variables
Objective To add variables to the working file from another SPSS data file.
Comment This illustrates the use of the Add Variables under Merge.
Problem The data file possums1.sav contains 2 data cases and 16 variables. The file possums2.sav
contains 3 new variables plus the common key variable patid with values 600 and 601. It is
necessary to combine the two sets of variables into one data file.
Activity 14.1 Open the file possums1.sav from the directory in which your SPSS example data sets are
stored.
Activity 14.2 Select Data>Merge Files>Add Variables.
Activity 14.3 Choose the file possums2.sav.
This file contains three variables id, height and weight with entries for patients with patid 600
and 601.
The following dialog window will be opened.
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