NOTE:  This page was created using SPSS version 19.0.1.

There are a few reasons why you may not be able to see your variables in some of the SPSS dialog boxes.   One possible reason is that your variable is a string variable and the dialog box will only accept numeric variables.  Another possibility is that your variable has a different measurement scale than the dialog box will accept.  A third possibility is that your variable does not have the appropriate role.  We will discuss each of these issues and how to resolve them.

If you are using syntax, you need to know if the variable is numeric or string (and you may need to convert string variables to numeric format), but the measurement level and variable role settings do no matter.  These assignments can be modified using syntax (as shown below).

String variables

Some dialog boxes show all of the variables in your data set, regardless of type of variable.  For example, you will see both numeric and string variables in the list of variables from which to choose.  Other dialog boxes, including the dialog box for the correlate command, will display only numeric variables.  Notice that although you can see the variable female in the data set, it does not appear in the list of variables that can be used in the correlation.

If we look at the Variable View window, we can see that the variable female is a string variable, even though it has values of "0" and "1".

There are several ways to convert string variables to numeric form.  For example, you could use the autorecode command, the recode command, or the numeric function with the compute command.  Below, we will use the autorecode command to convert the string variable female into the numeric variable female_num .

autorecode female / into female_num.
Please see our Introduction to SPSS Syntax 
seminar (section 7) for a more thorough discussion of these commands and 
examples.  Once the variable has been made into a numeric variable, it will 
appear in the dialog box.
Measurement level
On the right side of the Variable View window, you will see a column titled 
Measure.  There are three possible settings for numeric variables:  
nominal, ordinal and scale.  String variables can be either nominal or 
ordinal.  
The dialog boxes for automatic linear modeling, nptests 
(non-parametric tests) and genlinmixed use measurement level to determine 
which variables can be used in the various dialog boxes.
In the dialog box above, the yellow bars at an angel are scales and indicate 
that variable is a scale variable.  The three vertical bars indicate that 
the variable is an ordinal variable, and the three circles indicate that the 
variable is a nominal variable.
From the SPSS help file system:
Note: For ordinal string variables, the alphabetic 
order of string values is assumed to reflect the true order of the categories.  
For example, for a string variable with the values of low,
medium, high, the order of the categories is interpreted as high,
low, medium, which is not the correct order.  In general, it is more reliable to use numeric codes to 
represent ordinal data.
When reading data into SPSS, the following conditions are used to determine 
the measurement level.
Copied from the SPSS help file located at
http://127.0.0.1:4235/help/index.jsp?topic=/com.ibm.spss.statistics.help/overvw_auto_0.htm 
Condition
Measurement 
		Level
All values of a
		variable are 
		missing
Nominal
Format is dollar or custom-currency
Continuous
Format is date or time (excluding Month and Wkday)
Continuous
Variable 
		contains at least one non-integer value
Continuous
Variable 
		contains at least one negative value
Continuous
Variable 
		contains no valid values less than 10,000
Continuous
Variable 
		has N or more valid, unique values*
Continuous
Variable 
		has no valid values less than 10
Continuous
Variable 
		has less than N valid, unique values*
Nominal
* N is a user-specified cut-off value. The 
default is 24.
You can change the measurement level of a variable in the Variable View 
window.  Alternatively, the variable level command can be used to change the measurement level 
of variables.   
variable level id race schtyp (nominal)
 /ses (ordinal)
 /female prog read write math science socst (scale).
Also, the cutoff value (how many unique values a variable must have to be 
given a level of scale) can be changed in the Options dialog box (Edit -> 
Options -> Data tab).  
Variable role
The variable role command was added to SPSS in version 18.  This 
setting can be seen in the variable View window on the far right.  It is 
used by the dialogs of some commands to pre-select variables for analysis.  
You can modify a variable’s role either by changing it in the Variable View 
window or via syntax with the "variable role" command.  A variable’s role 
has no effect when running commands via syntax; it only matters when using the 
point-and-click interface of some of the newer commands in SPSS.
Some of the commands whose point-and-click interface uses the variable role 
are genlinmixed and automatic linear modeling. 
Here is a brief summary of roles.  This information is taken from the 
Command Syntax Reference Guide entry for variable role.  By default, 
all variables are assigned the input role. 
Input
predictor/independent variable
Target
output/outcome/dependent variable
both input and output (both DV and IV)
no role assignment
Partition
the variable will be used to partition the data into separate 
		samples for training, testing, and validation
Split
This is used with IBM SPSS Modeler.  This is not a variable 
		that will be used in to "split the file" in SPSS Statistics
The variable role command can be used to change the role of variables.
variable role
 /target write read
 /input math science ses schtyp
 /both socst.