1. Data Manipulation (with SQL)
HRP223 – 2009
October 12, 2009
Copyright © Leland Stanford Junior University. All rights reserved.
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2. Topics For Today Organization Sharing a SAS dataset Renaming
As .sas7bdat files or other formats
Renaming
Datasets
Variables
Subsetting a dataset
Select a few variables
Select a few records
SQL reports for a single table of data
Selecting/renaming variables
Applying labels and formats
Creating tables with SQL

3. Avoiding Spaghetti Code
Organization
Avoiding Spaghetti Code
Programmers refer to unstructured, poorly thought-through, unorganized code as spaghetti code. Your EG projects will literally look like a tangled mess of spaghetti if you do not structure them in advance.
Use several named process flows
Use lots of notes in the project
Include a lot of comments if you write code
This is bad.

4. Organization
Process Management
Typically you will have a process flow that creates the library and does importing from the source file(s) and does data cleaning and splits the data into subsets.
If you do different sets of analyses to the subsets, add in a process flow for each subset.
Create a dataset called analysis that has all the information used in the analysis.

5. Organization
You may want to link the library to the dataset and then uncheck Auto Arrange to have it show you the arrow.
Right click on the process flow and give it a meaningful name.

6. The Greater Right of the Left
Organization
The Greater Right of the Left
Your process flows should have the source of the data on the left. The left margin should have:
A note saying what the flowchart does
A code node that creates a toy dataset or a library (or libraries) that contains the data

7. Organization
A Good Process Flow

8. Organization in Programs
All my SAS code begins with the same header information.
The /* */ are used to mark large comments.

9. Specify where output will be stored.
Display manager deletes output text and log.
Do not show the name of the procedures in output.
Do X commands ASAP. Don’t show the date in output and reset page # to 1.
Delete graphics in the work library.
Make the folder where output will be stored if it does not exist. Delete what is there if it exists. Set file path to that directory.
Make a library to store output datasets.
Make a web page to display all output.
Make pretty graphics.
Run other programs.
Turn off graphics and output.

10. Sharing Data You can share SAS data sets just like Excel files.
Create a library.
Copy the data into the library.
If the data has formats associated with it, be sure to send the formats.
More on this on a later date.

11. Sharing
Exporting the Easy Way
Double click the data set you want to export and use the Export context dependent menu.
data humans;
input isDead $ age;
datalines;
true 20
false 45
false 21
true 67 ;
run;

12. With Code…. Create a library with the GUI or use the libname statement
Sharing
With Code….
Create a library with the GUI or use the libname statement
libname blah "C:\blah";
Write a little program:
proc copy in = work out = blah;
select humans;
run;

13. Sharing
This code is efficient.

14. Sharing
Alternatives
Novices underuse proc copy. Instead they typically write less efficient data steps. For example,
data blah.humans;
set work.humans;
run;
Or they may write:
data "C:\blah\humans.sas7bdat";

15. Sharing

16. Export Code for a Different Format
Sharing
Export Code for a Different Format
proc export outfile = "c:\projects\hrp223\lab1\humans.xlsx" data = blah.humans replace;
run;

17. Sharing
Note that you have to manually connect the code node to the right place in the flow chart and the exported item does not show up on the process flow.

18. Copy and Rename
Renaming datasets
If you want to copy and rename a file, use the GUI or write code.
Double click the data set.
Choose Query Builder from the context sensitive menu.

19. Renaming datasets

20. Renaming datasets
With code…
data blah.test;
set work.humans;
run;

21. Select a Few Variables From Fake Data
The next task is to select a couple of variables from a data set that has a LOT of variables.
If you get a premade dataset with lots of extra variables, you want to drop the ones you will never use. Do this as soon as you can.
First I will make some fake data. The data set will have a simulated test value filled into 6 “month” variables.

22. How to make a fake subject
Fake data
How to make a fake subject
Comments
data fakeData;
* make 12 empty numeric variables;
array month [12];
* put the record number into a variable named subject;
subject = _N_;
* repeat the code below 12 times;
do x = 1 to 12;
* put a random number from list #1 into month1, month2, etc;
month[x] = ranuni(1);
end;
* write the information to the fake dataData data set;
output;
run;

23. Fake data

25. Selecting variables and renaming
Rename and label variables
Selecting variables and renaming
You can use the Filter and Sort context sensitive menu to select a few variables.
To rename a variable or change how it prints in reports you need to use the Query Builder or write code.

26. Rename and label variables
Drag and drop the variables you want into the Select Data windowpane.
Click on a variable name. Then use the properties button to change the name and the display label.

27. Rename and label variables

28. Rename and label variables
I usually display the variable names instead of the labels.

29. Rename and label variables
What it did…

30. Notice where the ; is found. This is one long statement.
Rename and label variables
Data Step Version
Notice where the ; is found. This is one long statement.
data firstLast (keep = subject january june);
set fakedata2
(rename = (month1 = January
month6 = June));
label January = "First Month";
label June = "Last Month";
run;
* have subject apepar first by referencing it first;
subject = .;

31. SQL reports
Minimal SQL
Print a report showing the contents of variables from a single data set.
Note that there is no create table ____ as
Put a comma-delimited list of variables here or * for all variables.
Specify a library.table here.

32. SQL reports
What variables?
Typically you will use a coma delimited list but you can use an * to indicate that you want all variables selected instead of typing them all.
There is no syntax to specify variables based on position in the source files. That is, you can not specify that you want to select the 2nd and 7th variables (from left to right) or to select the first 3 variables.

33. SQL reports – selecting variables
Use of Minimal SQL
Note that the order of the list sets the order in the report (or the order in a new dataset).

34. SQL reports – rename/label
Renaming and Labels
You can rename a variable in the list with an as statement.
You can also specify variable labels.

35. SQL reports – format
Using Formats
Labels affect column headings and similar titles, and formats affect how values appear without changing the values themselves.
Notice the lowercase i. The capitalization is set when the variable is created.

36. Preview of User Defined Formats
SQL reports – format
Preview of User Defined Formats
Note the $ means a character format.

37. SQL tables
blah
Original table
New table.

38. SQL reports – table aliases
More Tweaks
The from line references tables which are in libraries. Complex queries require you to reference the table name over and over again. Instead of having to type the long library and dataset names repeatedly, you can refer to the files as an alias.
Print the column called dude from the table blah which is in the fakedata library.
Here the b. is optional because dude is only in one table (the query only uses one table).

39. Rename label and format variables
Data Step Version….