Abbreviated as SPSS according to AbbreviationFinder, Statistical Package for the Social Sciences has a file system in which the main one is the data files (extension. SAV). Apart from this type there are two other types of frequent use:
- Output files (output, extension. SPO): these display all the information on data manipulation that users perform through command windows. They are capable of being exported with various formats (originally HTML, RTF or TXT, currently version 15 incorporates the export to PDF along with the XLS and DOC formats that were already in version 12)
- Syntax files (extension. SPS): Almost all SPSS windows have a button that allows pasting the process that the user wishes to perform. The above generates a syntax file where all the instructions carried out by the SPSS commands are stored. This file is susceptible to being modified by the user. Many early SPSS users write these files instead of using the program’s paste system.
There is a third type of file: the script file (extension. SBS). This file is used by the most advanced users of the software to generate routines that allow automating very long and / or complex processes. Many of these processes are not usually part of the standard outputs of SPSS commands, although they do start from these outputs. Much of the functionality of the script files has now been taken over by the insertion of the Python programming language into the SPSS syntax routines. Procedures that previously could only be done through scripts can now be done from the syntax itself.
When the program is installed it brings a certain number of examples or utilities of almost all the files in question. These are used to illustrate some of the usage examples of the program.
SPSS data file
Data files in SPSS format have the extension in Windows. SAV. When opening a data file with SPSS, we see the data view, a table in which the rows indicate the cases and the columns the variables. Each cell corresponds to the value that a certain variable takes in a certain case.
In addition to this data view, in the latest versions of the program there is a variable view in which the characteristics of each one are described. In this view, the rows correspond to each variable and the columns allow us to access their characteristics:
- Name, limited to 8 characters.
- Type of variable (compare this list of options with the types of existing statistical variables)
- Numeric, number in standard format)
- Comma decimal, number with commas every three places and with a period as a decimal delimiter
- Decimal point, number with points every three positions and with a comma as the delimiting limit of the decimals.
- Scientific notation, a number that is expressed in a format such that it is followed by an E and a number that expresses the power of 10 to which the previous numerical part is multiplied
- Dollar currency, numerical format with which dollar amounts are expressed
- User currency, numerical format with which amounts are expressed in the currency defined in the currencies tab of the “Options” dialog box
- Character string or alphanumeric variable
- Total size
- Decimal part size
- Variable label
- Labels for values
- Missing values
- Space it occupies in the data view
- Variable alignment in data view
- Measurement scale.
Some users overlook the characteristics of variables when working in the database. However, when using scripts or Python, the characteristics of the variables can take great relevance in the construction of ad-hoc procedures.
SPSS syntax file
These syntax files can be generated with the help of the program itself, since in almost all windows where tasks are carried out in SPSS there is a “Paste” button. This button closes the window in question and saves the syntax of the actions selected in that window. Once this file is saved, it is subject to modification.
The syntax as presented below was produced directly with SPSS. This program gives a readable format to the syntax, a format that the software in some cases does not require for its correct use.
Another peculiarity of the SPSS syntax is that they are not “case sensitive”. Before which it is common to see syntax written only in uppercase, only in lowercase or a combination of each user. This situation is modified for those people who make use of Python within its syntax, since it is a sensitive language to variations between upper and lower case. This forces these users to write syntax more carefully.
The following example illustrates how to open a data file using syntax and how to carry out a frequency and a contingency table with data from one of the example files installed by the program.
* This is a comment, it must be preceded by an asterisk and ended with a period.
* Open the Tomato.sav file.
FILE = ‘C: \ Program Files \ SPSS \ Tomato.sav’.
* Generate a table with the frequencies of the fertilizer variable.
VARIABLES = fert
/ ORDER = ANALYSIS.
* Generate a contingency table with the variables initial height and fertilizer.
/ TABLES = initial BY fert
/ FORMAT = AVALUE TABLES
/ CELLS = COUNT
/ COUNT ROUND CELL.