Practical Data Management and Statistical Computing (BioEp691F)

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Outline: Lec1 Lec2 Lec3 Lec4 Lec5 Lec6 Lec7 Lec8 Lec9 Lec10
Lectures: Lec1 Lec2 Lec3 Lec4 Lec5 Lec6 Lec7 Lec8 Lec9 Lec10

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Lecture 3

• Using a SAS data set again in the same SAS Session
  • Example:
    • lec1sm1.sas reads in a simple SAS data set.
    • dmse99p5.sas (uses previously created temporary SAS data set to create another SAS data set)
• Saving a Permanent SAS Data set
  • dmse99p6.sas creates permanent SAS data set and includes a LABEL

Usually we will read in data that has been stored in a separate ASCII file with a file name. In SAS, we specify the name of the file, and its location with in INFILE statement. Rather than including the data directly in the SAS program, there is reference to data file name and location.

• Example:
  • Review the program lec1sm5.sas
  • Suppose data for the Weight Club has been stored in an ASCII file called lec1sm2.txt on the C:\DATA directory. We read the data into SAS from this file with the program dmes99p3.sas.

Avoiding Problems when Downloading a Copy of ASCII Data from the WEB to an ASCII data file

When saving data from the WEB, formating characters that are not visible may be included in the saved data set that later can cause problems when reading the data into SAS. If data are saved in a particular manner, these formating characters will be deleted in the saved file. We illustrate two ways in which ASCII data can be saved from the WEB, with formating characters deleted.

• Example
  • Method 1 to save lec1sm2.dta on the C:\DATA directory from the WEB:
    • Open the data set by clicking on it in your WEB browser.
    • Open MS WORD. Then, in Netscape, use SELECT ALL from Edit Menu, and then COPY to Copy data into MS-WORD. Then save the file as a .txt file with carriage returns (ie. lec1sm2.txt)
  • Method 2 to save lec1sm2.dta on the C:\DATA directory from the WEB:
    • Open Notepad (to open, from Start, select Programs, and then Accessories). Then, in Netscape, use SELECT ALL from Edit Menu, and then COPY to Copy data into Notepad. Then save the file as a .dat file with carriage returns (ie. lec1sm2.dat)
• Examine the saved data using NOTEPAD

Problems When Downloading an ASCII data file from the WEB:

When saving data from the WEB, formatting characters can cause problems. We illustrate an example of the problem here.

• Save lec1sm2.dta on the C:\DATA directory using the following:
  • Open the data set by clicking on it in your WEB browser.
  • Click on the FILE pull-down menu in your WEB browser, and then select SAVE AS, placing the file in the C:\DATA directory with the name lec1sm2.dta.
• Copy the program dmes99p4.sas into SAS, and run the program.
• Examine the program log (dmes99p4.log)

Discussion: The log file indicates some errors in the data that prevent SAS from reading the last variable. Inspecting the data in NOTEPAD reveals no problem. What's wrong? One possibility is that there are hidden characters (ASCII characters that do not appear on the computer screen in programs like NETSCAPE, or NOTEPAD) that are contained in the data set, and confuse SAS. By going through the steps above, other software will delete these special characters. We can identify some of these characters by reading the saved data into the SAS program window.

• In SAS, open the data set lec1sm2.dta in the program window. You should see some characters that are not alphanumeric.

• One of the best ways to type in data
• Require data lined up in columns, easily proof read.
• Decimals and decimal points need to be consistent (see lec3sm1a.sas, with output given by lec3sm1a.lst)
• Reading data in column input
  • Example 1 (lec3sm1.sas) (see SAS Language Manual, p409)
• Determining Columns for writing INPUT statement using Column input.
  • Example 2. (lec3sm2.sas)
    • INFILE Statement with an OBS= option and CARDS option
    • LIST statement
  • Then, use the results to write the INPUT statement (lec3sm3.sas)

• INFILE with FIRSTOBS= option.
• PROC CONTENTS

• WEB: Read WEB pages on SAS1 -Basic, Intro and Data In
• Chapter 9: Data Documentation: INFILE, p377 (intro only), SAS Language , Reference Version 6 First Edition.
• Chapter 3 Starting with Raw Data (column input)(pp39-44).SAS Language and Procedures, Usage Version 6 1st edition.
• Chapter 9: Data Documentation: INPUT, Column, p407-409, SAS Language , Reference Version 6 First Edition.
• Chapter 9: Data Documentation: INFILE, FIRSTOBS= ,OBS= option, p382, 384, SAS Language , Reference Version 6 First Edition.
• Chapter 9: Data Documentation: LIST p437-438, SAS Language , Reference Version 6 First Edition.
• Chapter 12: PROC CONTENTS, pp194-199, SAS Procedures Guide, Version 6, Third Edition.