Sometimes it is convenient to loop through two lists of variables. For example, you may want to run several simple regressions. While syntax could be written to specify each dependent and independent variable to be used, it would be nice to simply provide a list of the dependent variables and a list of the independent variables to be used and let SPSS loop through the two lists to run the regressions. Below is the syntax for doing this task. Because we are looping through more than one variable, we will need to use Python.

Please note that in order to use the syntax on this page, you need to have both Python and the SPSS Python plug in installed. If you are using SPSS versions 17, 18 or 19, you should install Python version 2.x. You can download Python for free from the Python website. You can obtain the SPSS Python plug in from the SPSS Developer Central website. For these examples, we will use the elemapi2.sav data set. We have not included any of the output because of its excessive length.

## Example 1: Listing each variable to be used

In our first example, we will explicitly state the variables that we want to
use as the dependent and independent variables. So in the first simple
regression, the dependent variable will be **api00** and the independent
variable will be **mobility**; in the second simple regression, the dependent
variable will be **api99** and the independent variable will be **avg_ed**;
in the second simple regression, the dependent variable will be **growth**
and the independent variable will be **full**. We also need to state the
name and path of the data set that we wish to use.

begin program. import spss, spssaux spssaux.OpenDataFile('d:\data\elemapi2.sav') dlist = ['api00', 'api99', 'growth'] ilist = ['mobility', 'avg_ed', 'full'] ddim = len(dlist) idim = len(ilist) if ddim != idim: print "The two sequences of variables don't have the same length." else: for i in range(ddim): mydvar = dlist[i] myivar = ilist[i] spss.Submit(r""" regression /dependent %s /method = enter %s. """ %(mydvar, myivar)) end program.

We start by using the SPSS **begin program** command. This command
indicates that code from an external coding language (i.e., Python) will follow. On the
second line, we tell Python to import the both the **spss** and the **
spssaux** modules; these allow Python to interact with SPSS. On the third line, the path and file name of the data file must be specified.
On the fourth line, we specify the variables to be used as dependent variables
in the regressions. Each variable name must be enclosed in quotes, and the
names must be separated by commas. Square brackets are used to enclose the
list. The independent variables are specified on the fifth line in the
same way. Each of these lists are put into an array. We called the
array of dependent variables **dlist** and the array of independent variables
**ilist**. To check that the two lists have the same number of
variables, we we obtain the length of each list, and if they are not equal, we
use the Python command **print** to display the message “The two
sequences of variables don’t have the same length.” If the two lists have
the same number of variables, then we move to the loop. We complete the program
with the SPSS **end program** command.

Within the loop, **i** is the counter that ranges from 1 to the value of
**ddim**. The Python variables **mydvar** and **myivar** contain
the dependent and independent variables for the current count of the loop.
The values of these variables are the strings that are substituted for %s in the
**regression** command. The values (strings) of %s are provided at the end of
the command with %(mydvar, myivar)). The first occurrence of %s
corresponds to the first variable listed in %().

The SPSS commands to be executed are given within the **spss.Submit**
function. In this example, we have only the **regression** command, but
more commands can be listed. Like all SPSS commands, the commands listed
must end in a period. The triple quotes are used to comment out the line
brakes. (In other words, “”” denotes a comment in Python.) Also note
that Python is very particular about how the line of the command are indented.

## Example 2: Specifying the variable lists using a range

In this example, a range of variables is used to specify the variable lists.
In other words, only the first and last variable for each list is needed.
This is very convenient if there are many variables to be used as dependent and
independent variables. However, the variables in each set (i.e., the set
of dependent variables and the set of independent variables) need to be
contiguous. In other words, all of the dependent variables need to be
side-by-side in the dataset, and all of the independent variables need to be
side-by-side in the dataset. Of course, the two sets of variables do not
have to be side-by-side. To tell Python about the list of variables, the
**spssau.VariableDict()** function is called, and the values in that
dictionary are placed in the object **vdict**. The Python variable **
dlist** contains the values (i.e., variable names) of the dependent variables,
and the Python variable **ilist** contains the values of the independent
variables. The rest of the program is the same as described in the example
above.

begin program. import spss, spssaux spssaux.OpenDataFile('d:\data\elemapi2.sav') vdict=spssaux.VariableDict() dlist=vdict.range(start="api00", end="ell") ilist=vdict.range(start="grad_sch", end="enroll") ddim = len(dlist) idim = len(ilist) if ddim != idim: print "The two sequences of variables don't have the same length." else: for i in range(ddim): mydvar = dlist[i] myivar = ilist[i] spss.Submit(r""" regression /dependent %s /method = enter %s. """ %(mydvar, myivar)) end program.

## Example 3: Expanding the strings in the loop

Sometimes the combination of dependent and independent variables is not what you
expect. The **set mprint on** command can be used to display
the commands as they are executed. Hence, the SPSS **regression**
commands are printed in the output file as they would if you just using the
**regression** command without the loop, Python, etc.

set mprint on. begin program. import spss, spssaux spssaux.OpenDataFile('d:\data\elemapi2.sav') vdict=spssaux.VariableDict() dlist=vdict.range(start="api00", end="ell") ilist=vdict.range(start="grad_sch", end="enroll") ddim = len(dlist) idim = len(ilist) if ddim != idim: print "The two sequences of variables don't have the same length." else: for i in range(ddim): mydvar = dlist[i] myivar = ilist[i] spss.Submit(r""" regression /dependent %s /method = enter %s. """ %(mydvar, myivar)) end program. set mprint off.

## Example 4: Labeling the output with the Python print command

The output can be very long, especially if there are many regressions to be
run. There are at least two ways that you can have a title at the
beginning of each regression output indicating what the dependent and
independent variables are. One method is to use the Python **print**
command. The plus signs are used to tell Python that other text is to be
included, and the entire message is enclosed in quotes. The output from
the Python **print** command is displayed as a log entry in the SPSS output.

begin program. import spss, spssaux spssaux.OpenDataFile('d:\data\elemapi2.sav') dlist = ['api00', 'api99', 'growth'] ilist = ['mobility', 'avg_ed', 'full'] ddim = len(dlist) idim = len(ilist) if ddim != idim: print "The two sequences of variables don't have the same length." else: for i in range(ddim): mydvar = dlist[i] myivar = ilist[i] print ('Dependent variable is '+mydvar + ' and the independent variable is '+myivar + '.') spss.Submit(r""" regression /dependent %s /method = enter %s. """ %(mydvar, myivar)) end program.

## Example 5: Labeling the output with the SPSS title command

If you would rather have a page title for each regression, you can use the
SPSS **title** command. This is included in the loop immediately before the **
regression** command. As with the **regression** command, %s is used
to provide the variable names. Note that in the second to last line of the
program, we have added two more arguments. Now, the first **mydvar**
refers to the first %s in the **title** command, and the first **myivar**
refers to the second %s in the **title** command. The second **mydvar**
refers to the first %s in the **regression** command (on the **dependent**
subcommand), and the second **myivar** refers to the second %s in the **
regression** command (on the **method** subcommand).

begin program. import spss, spssaux spssaux.OpenDataFile('d:\data\elemapi2.sav') dlist = ['api00', 'api99', 'growth'] ilist = ['mobility', 'avg_ed', 'full'] ddim = len(dlist) idim = len(ilist) if ddim != idim: print "The two sequences of variables don't have the same length." else: for i in range(ddim): mydvar = dlist[i] myivar = ilist[i] spss.Submit(r""" title "The DV is %s and the IV is %s.". regression /dependent %s /method = enter %s. """ %(mydvar, myivar, mydvar, myivar)) end program.## For more information

- For more information looping through lists of variables using Python, please see SPSS FAQ: How can I write a Python program to rename variables in SPSS? .
- For more information on renaming variables dynamically using SPSS loops, please see SPSS Code Fragment: A few SPSS loops for renaming variables dynamically .