1.0 SPSS commands used in this unit
|display||displays attributes of the data set|
|variable labels||labels a variable|
|value labels||adds labels to values of a variable|
|autorecode||recodes variables and automatically adds value labels|
|rename variables||renames variables|
|document||adds a document to the data set|
|compute||creates new numeric variables|
|summarize||calculates descriptive statistics|
|aggregate||creates new variables with aggregated data|
2.0 Demonstration and explanation
Let’s begin by opening the data file.
File Open select the C: drive, the spss_data folder, and hs0.sav
It is often useful to see information regarding the data file, such as the number of cases and variables, any type of labels, etc.
File Display Data File Info... Working file select c:/spss_data/hs0.sav
2.1 Reordering variables
Reordering variables in the data file is helpful both for organizational reasons as well as to minimize the amount of scrolling you need to do in order to see the variables that you are working with. We will use the “cut and paste” method of reordering the variables.
highlight id Edit Cut highlight the variable that will appear after the newly-placed variable, say gender. Highlight gender Edit Insert variable Edit Paste
2.2 Adding variable and value labels
Adding variable labels is a very useful data management strategy, and we encourage you to take the time to do this when you input a data set or receive a data file.
Click on "Variable View" tab (in the lower left corner) for schtyp, type in the label "The type of school the student attended.".
2.3 Changing a string variable to a numeric variable
If we click on the “Variable View” tab, we can see that the variable prgtype is a string variable, and this may cause some difficulty when we are using this variable in analyses. So let’s create a numeric version of this variable.
Transform Automatic recode... select prgtype type in a name for the new variable (prog) and click on the "Add New Name" button
Add a variable label to the variable that we just created.
Add a variable label to prog.
2.4 Renaming variables
Renaming variables is easy. We can rename the variable gender to female, and then add variable and values labels.
Click on the "Variable View" tab and change gender to female
Click on "Variable View" tab (in the lower left corner). Change gender to female, type in the label "The gender of the student.", and add the value labels.
2.5 Recoding values
Suppose that we would like to recode some values of a variable. For example, we might want to change the 5s to missing. If you like, you can use the frequencies command before and after the recoding to see the changes. You may also want to include some reminders of this change. We can create a document for this purpose.
Transform Recode Into same variable... select race click "Old and New Values" and type in the old value (5) and the new value, in this case, click on the "System-missing" radio button, and then click on "Add", then "Continue", then "OK"
2.6 Creating a new variable
There are many ways that you can create a new variable. One way is to use a numeric expression. For example, let’s create a variable called total that will be the sum of the reading, writing and math scores.
Transform Compute... type in the name of the new variable, total, (called the "Target Variable") and the numeric expression that will create the variable: read + write + math
Analyze Descriptive Statistics Descriptives... select total
It might make more sense to add the social studies score to the total rather than the math score, so let’s change that.
Transform Compute... type in the name of the new variable, total, (called the "Target Variable") and the numeric expression that will create the variable: read + write + socst
Now let’s summarize the variable that we have just created.
Analyze Descriptive Statistics Descriptives... select total
We will recode total to become grade as shown below.
Transform Recode... Into different variables... select total as the "input -> output variable" type grade as the output variable change click "old and new values" click on "range: lowest thru" and type 80 as the value and type 1 as the new value click on "range" and continue to enter the values according the table below. For the last category, click on "range: thru highest" recoding total into grade: lowest - 80 = 1 80 - 110 = 2 110 - 140 = 3 140 - highest = 4
Let’s label the data set itself so that we will remember what the data are. We can also add some notes to the data set.
Syntax must be used to label data. The command is: file label "High School and Beyond".
Utilities Data File Comments The variable gender was renamed to female; The values of race coded as 5 were recoded to be missing.
Finally, let’s make z-scores of some of our variables. There are at least two way that you could do this. If you remember the formula for creating z-scores and you know the mean of the variable, you can use the transform -> compute function as we did before. Another way to create the z-scores is shown below.
Analyze Descriptive Statistics Descriptives... select read click on the box "Save standardized values as variables"
2.7 Using functions
SPSS has many functions that you can use to create new variables. First we will create a new variable that contains the mean of read for each level of ses.
Data Aggregate select ses as Break Variable(s) select read as Summaries of Variable(s) click on Name and Label and type rmean as name
Next, we will create a new variable that contains the mean of several variables. Please note that there will be a mean for observation 9 even though it has a missing value for science.
Transform Compute Variable type row_mean in Target Variable box select Statistical from Function group box double click on mean from Functions and Special Variables box double click or type read, write, math, science in the Numeric Expression box
Before we leave this unit, let’s save the data set.
File Save As... hs1
3.0 Syntax version
* open the data file. get file "c:spss_datahs0.sav". * ordering the variables in a way that makes sense. save outfile = "c:spss_datahs01.sav" / keep id gender all. get file "c:spss_datahs01.sav". display variables. * adding variable and value labels to schtyp. variable labels schtyp "the type of school the student attended.". value labels schtyp 1 "public" 2 "private". display dictionary /var = schtyp. list schtyp /cases from 1 to 10. * changing prgtype from a string to a numeric variable (called prog). auto recode variables = prgtype /into prog /print.
* adding the variable label. variable labels prog "The type of program in which the student was enrolled.". rename variables (gender = female). variable labels female "The gender of the student.". value labels female 1 "female" 0 "male". display dictionary /var = female. list female /cases from 1 to 10. * recoding race = 5 to missing. frequencies var = race. recode race (5 = sysmis). frequencies var = race. * adding notes to the data set and viewing the notes. document the variable gender was renamed to female. document values of race coded as 5 were recoded to be missing. display document. * creating a variable that is a total of some of the * test scores. compute total = read + write + math. summarize var = total. * creating a variable that is a total of the reading * writing and social studies test scores. compute total = read + write + socst. variable labels total "the total of the reading, writing and social studies scores.". * creating a variable that is a total of some of the test scores. summarize var = total. display dictionary /var = total. * assigning some letter grades to these test scores. recode total (0 thru 80=0) (80 thru 110 =1) (110 thru 140=2) (140 thru 170=3) (170 thru 300=4) into grade. execute. value labels grade 0 "f" 1 "d" 2 "c" 3 "b" 4 "a". variable labels grade "these are the combined grades of reading, writing and social studies scores.". display dictionary /var = grade. list read write socst grade /cases from 1 to 10. file label "High School and Beyond". document The variable gender was renamed to female; The values of race coded as 5 were recoded to be missing. display document. * there is another way to create variables * in SPSS that uses special functions. descriptives var = read /save. summarize var = zread. list read zread /cases from 1 to 10. aggregate /break = ses /rmean = mean(read). save outfile "c:spss_datahs1.sav".
4.0 For more information
- SPSS Programming and Data Management, Fourth Edition
- Chapter 6
- SPSS Learning Modules
- SPSS Frequently Asked Questions