Statistics 212/601/651/652/659

Guide to SAS on the PC

Following is an outline to help you run some basic SAS analyses on the PC. I will eventually add more details on SAS procedures. I am assuming that you have started SAS and the windows are visible on your PC. There are three windows:

Running Batch SAS

  1. Create a file with a .sas extension that contains your SAS program, for example, prog.sas .

  2. Load the program into the PROGRAM EDITOR by clicking on the File menu and then on Open . Highlight prog.sas and click on OK . Alternatively you can type your program into the PROGRAM EDITOR.

  3. To run the program, click on Locals and then on Submit . Alternatively, click on the button with the running figure on the tool bar.

  4. Check the LOG Window to see if there are any errors.

  5. If not, the SAS analysis is available in the OUTPUT Window. The results should be saved to a file, say prog.lst , by clicking on File and then on Save As . You can use the editor or word processor of your choice to incorporate the output into your writeup. To get rid of output that you no longer need, choose Edit and Clear Text .

  6. If there are some errors, you can recall the program by clicking on Locals and then on Recall Text . You can correct your errors using the PROGRAM EDITOR. Be sure to save the corrected program by clicking on File and then on Save .

Creating a SAS Program

The SAS programs consists of 3 parts:
  1. data step
  2. data values
  3. SAS procedures
SAS statements end with semicolon (; ). An asterisk (* ) at the beginning of a SAS statement causes the statement not to be executed and to be treated as a comment. Following is a simple SAS program which will explained in the text:

data name;
input x y;
cards;
8 10
12 14.2
16 16.3
20 24.3
24 22.7
proc print;
proc plot; plot y*x;
proc reg; model y=x/r cli clm;
run;

Data Step

The data step defines the variables in the dataset. A basic data step is the following:

data name;
input x y;
cards;

The following three statements are necessary:

  1. data name; This says that a data set called name is to be created.
  2. input x y; This says that the data will be read in with an x value followed by a y value on each line. A character variable name is followed by a dollar sign ($).
  3. cards; This says that the data values follow.
One can add expressions between the input and cards statement to create new variables that are functions of x and y. For example, ylog=log(y); will create a new variable called ylog that is the natural logarithm of y.

SAS will read only as many values as there are variables in your input statement. It then read values on the next line. This continues until SAS finds a program statement. Thus, each line in the data set will consist one observation of each of the variables in the input list. To have more than one observation per line, place the characters @@ before the semicolon in the input statement.

Data Values

The data values are entered with each line consisting of a single observation of the variables given in the input statement. The values of the variables are separated by one or more blanks. A simple set of data follows:

8 10
12 14.2
16 16.3
20 24.3
24 22.7

SAS Procedures

Any number of SAS procedures can be used to analyze the data. Each procedure begins with a proc statement followed by the name of the procedure. Following is an example of a short sequence of procedures used for simple linear regression:

proc print;
proc plot; plot y*x;
proc reg; model y=x/r cli clm;
run;


Importing Data into SAS

SAS provides for the import of text files, Excel files, and other files. You start out by choosing Files and then Import Data... . The SAS Import Wizard will appear. On this window choose the type of file such as Excel (*.xls) or tab-delimited text file (*.txt). Then click on Next. The next box asks for the location of the file. Either type this in or click on Browse and find the file where you stored it on the hard drive. After the name of the file appears in the box, click on Open . This will take you back to the previous box. You check that you have chosen the correct file and click on Next . You are now asked for the SAS destination. You will usually use the default WORK library. You enter the name of the dataset in the empty box labelled "Member". Click on Next . You then click on Finish which completes the importing of the data. You can then analyze the data using either batch SAS or interactive data analysis.

SAS INSIGHT--Interactive Data Analysis

INSIGHT provides a menu-driven approach to analyzing data. In particular, you can obtain very good graphs using INSIGHT. You must first create the desired data set. One way is to use a data step as above followed by some procedure, such as proc print;. Alternatively, you can import the data set into SAS.

Version 6.12 To start INSIGHT, choose GLOBALS followed by ANALYZE and INTERACTIVE DATA-ANALYSIS . To load the data set you just created, choose WORK and then the desired dataset. INSIGHT will place your data into a spreadsheet.

Versions 8.0 and 9 To start INSIGHT, choose SOLUTIONS followed by ANALYSIS and INTERACTIVE DATA ANALYSIS . To load the data set you just created, choose WORK and then the desired dataset. INSIGHT will place your data into a spreadsheet. To start To create new variables from existing ones, click on the column for a given variable. Then click on EDIT and VARIABLES and choose the desired transformation. A new variable will be place in the spreadsheet.

Choose the desired analysis from the ANALYZE menu.


Descriptive Statistics Using INSIGHT

The data set for the regression should be placed into INSIGHT using the above procedure. Next choose Analyze and Distribution (Y) . Click on any variable of interest and then on the Y box. Continue until you have all the variables of interest. By clicking on the Output box, you can choose additional statistics and graphs for the output. Click OK in the Output window. Then click OK to obtain the descriptive statistics.


Simple Linear Regression Using INSIGHT

The data set for the regression should be placed into INSIGHT using the above procedure. Next choose Analyze and Fit (Y X) . A box containing all the variables in your data set will appear. Click on the name of the response (Y variable) and then on the Y box. Next click on the name of the predictor (X variable) and then on the X box. To choose various output options, click on the Output box. You can obtain residuals, predicted, and various diagnostic variables by clicking on the Output Variables box.

To run the regression analysis, click on Apply .


Printing Output from INSIGHT

One can copy the output from INSIGHT into a Microsoft Word document and then print the resulting document. First, obtain the desired analysis. Next, hold down the left mouse button and move the cursor over the boxes containing the desired output. After the mouse is released, the outlines of the selected boxes should be dark. Then choose File-Save-Graphics File . Give the file a name (on your diskette) ending with the "gif" extension such as trial.gif, choose GIF and grey scale, then OK. Next go to the Word window. Choose Insert-Picture-From File . Click on the desired file and OK . The SAS analysis is now part of your Word document. You can modify the size of the picture and its location within Word.